I realized some demons have weak points and it's much easier/fun to slay them by abusing those weak spots especially when you play on harder gamemodes such as insane or heroic mode. I believe it would be useful for casual players who want a better experience or for hardcore achivement collectors. I will put pictures of each demon marked weak spots and armor. I won't mark demons' heads because you already know landing headshots deal much more damage in any shooter game. "Slashable parts" could be destroyed by your katana(sword) or with gunshot. Demons usually lose an ability and gain a relatively weaker one after losing one of their body parts. It's usually worth to destroy them piece by piece for maximum efficiency. It's also more fun!

Katana
This is your primary weapon. Extremely effective against most type of enemies(except some boss fights) and it has no ammo. Try to prioritize your Katana for the most effective demon slaying experience. Your katana gets stronger and stronger by urther you go in the story. It provides infinite shurikens to throw at enemies by pressing Q, dealing a little damage.
Tier I: +%20 damage
Tier II: %5 chance to drain hp from enemies
Tier III: Katana swings send waves of ki energy

Tosainu Type 13 Revolver
This pistol is good at quickly dealing high damage to single target. It has a slow fire rate but you can shoot much faster after unlocking the RMB ability of the gun. You can use this against slow targets and mostly in boss fights.
Extended Barrel: Increases accuracy by 50%
Lightweight Cylinder: Increases rate of fire by 20%
Single Action: Adds rapid fire by pressing RMB

ZP-1 PDW
That's the basic SMG. It's very effective against weaker type demons, especially the mobile ones. It's easy to land shots since it has a low recoil. Don't use this against greater demons because of its low damage output. Might be useful against in some boss fights tho.
Laser Sight: Increases accuracy by 25%
Match Grade Barrel: Increases damage by 25%
Akimbo: Alternate fire that inflicts more damage with a second ZP-1 PDW by pressing RMB

Mamushi Type-14 Crossbow
Crossbow is extremely good against all type of enemies, especially after unlocking the charged bolts upgrade. It has a high damage, good accuracy and able to collect the ammo back from corpses. You can kill bosses and greater demons with few bolts. You can use it as a grenade launcher against demon hordes after unlocking the upgrade needed for that.
High-Strain Systems: Adds a charge up mechanic which increases shot damage up to 4 times
Extended Mag: Holds 25% more bolts
Sticky Bombs: Turns up to 3 arrows at once into sticky mines by pressing RMB

ZICS-C Shotgun
This is a decent gun with high damage in close range. You can one shot kill the basic demons while it takes a few shots to take down the greater demons. It's nearly useless in harder game modes such as insane and heroic.
Quad pack: Adds two additional barrels. Increases damage
Double Shell Clips: Adds the ability to load two shells at once, lets you reload faster
Firestorm: Adds the ability to unload all barrels at once by pressing RMB

Onibi Flamethrower
This is probably the worst gun in the game. You can try using it if you feel like it but it's much weaker than other weapons. It becomes a bit better after unlocking the RMB upgrade.
Extended Fuel Tank: Increases fuel storage up to 30%
Inferno Mix: Increases damage up to 25% and enemies now will start to panic after lit on fire
Fire Bombs: Turns flamethrower into an incendiary bomb launcher by pressing RMB

Yari Type-24 Rocket Launcher
Rocket Launcher one shot kills the lesser demons and it takes only few shots to kill the greater ones. This is an easy to use overpowered weapon but its downside is expensive ammo cost and low projectile velocity. It's useless in most boss fights.
Multi-Launch: Adds the ability to shoot up to 3 missiles at once
Heavy Warheads: Increases missile explosion radius by 30%
Laser Guidance: Adds the ability to guide shot missiles by pressing RMB

Picking up the right skills improves your ability to kill demons but you will unlock them all eventually so pick them based on your playstyle. I recommend focusing on Katana Mystery, Restoration and Movement first.

Katana Mystery
Divider of Heavens
This is the best skill for dealing damage. You can use it against any kind of demon. It has no ammo or mana so feel free to spam it. It deals AOE damage in a small area.

Circle of Iron
It deals damage around you by 360 degrees, pretty good against lesser demons especially when you are surrounded by them.

Wing of Crane
It lets you send projectiles from your katana, very nice alternative to firearms. These projectiles goes through demons so you can kill more than one demon with each swing. It goes through shields as well.

Kenshi
Increases ki strike damage by 20%.
Kensei
Increases ki strike damage by 50%.

Aswang Hunger
KI strikes restore some health.

Restoration
Medic
Health Packs heal +20 HP above maximum health.
Doctor
Health Packs heal +40 HP above maximum health.

Drain Soul
+50% damage and 5 seconds window in which killing an enemy will revive you.
Soul Hunger
+50% longer duration for drain soul.

Soulseeker
+20% chance of restoring souls appearing.
Souleater
+30% chance of restoring souls appearing.

Knowledge
Demonslayer I
Increases damage against lower demons by 10%.
Demonslayer II
Increases damage against lower demons by 20%.

Godslayer I
Increases damage against higher demons by 10%.
Godslayer II
Increases damage against higher demons by 10%.

Headhunter I
Warlord drops his head, which can be used as a weapon.
Headhunter II
Increases heads killing rate by 30%.

Movement
Inner Reserve I:
Increases stamina by 20%.
Inner Reserve II:
Increases stamina by 50%.
Inner Reserve III:
Increases stamina by 100%.

Quick Recovery I
Increases stamina regeneration rate by 20%.
Quick Recovery II
Increases stamina regeneration rate by 50%.

Divine Wind
Increases sprint speed by 20%.

Luck
Heart On
Increases chance of demons dropping hearts by 50%.

Richman I
Find 10% more money.
Richman II
Find 20% more money.

Armed
Find 10% more ammo.
Dangerous
Find 20% more ammo.

Critical Strike
Increases chance for double damage by 5%.

Mind
Fire Resistant
Gives immunity to damage caused by open flames including the fire from Onibi Flamethrower.

Rage I
When under 30 HP, the damage dealt by Wang increases by 30%.
Rage II
When under 30 HP, the damage dealt by Wang increases by 60%.

Control Pain I
Increases base HP by +10.
Control Pain II
Increases base HP by +20.
Control Pain III
Increases base HP by +30.

They are free to use, there is no mana in this game so you can spam powers as much as you want. Only problem with spamming them is: the more you use them, the more demons get enraged. Try using these only when necessary instead of randomly spamming them. Healing is the best one.

Healing
Peacocks Blessing
Heals 45 to 65% of maximum health in 5 seconds but makes Wang more vulnerable to damage.

Invigorating Dew(tier I)
Heals up to 60% of lost health.
Healing Rain(tier II)
Heals up to 80% lost health.

Protective Fan(tier I)
Receiving damage no longer breaks channeling.
Soaring Feather(tier II)
Channeling time decreased to 4 seconds.

Shockwave
Tiger's Roar
Knocks down enemies in a 4 meter range, rending them unable to get up for 3 seconds.

Tiger's Pounce(tier I)
Allows Lo Wang to stun his enemies for up to 5 seconds.
Deafening Roar(tier II)
Increases Shockwaves range to 6 meters.

Calming Breeze(tier I)
Makes demons less eager to attack Lo Wang.
Peaceful Storm(tier II)
Shockwave removes demon rage.

Protection
Dragon's Scales
Blocks 40% frontal melee damage.

Dragon's Endurance(tier I)
Blocks all types of attacks.
Dragon's Embrace(tier II)
Blocks damage from all directions.

Reflecting Scales(tier I)
Shield gains 20% chance to knock down enemies.
Iron Skin(tier II)
Shield blocks 50% of the incoming damage.

Flux
Water Trap
Releases a 20 meter line, which lifts lesser demons in the air for up to 4 seconds.

River Dragon(tier I)
Casting new waves no longer releases previously captured demons.
Koi Snare(tier II)
Maximum Flux duration increased to 6 seconds.

Calm Pool(tier I)
Effects lesser demons in rage too.
Abyssal Stream(tier II)
Flux range increased up to 30 meters.

Armor: None
Hit Points: Lowest
Loot: Demon Hearts(weapon)
Range: Melee
Speed: Medium
Special Ability: Mobility. Can climb to walls, dodge and jump
Slashable Parts: Arms, legs, torso, head
Threat: 🟢 ⚫ ⚫ ⚫ (low)
Info: Crawlers are the weakest enemies in this game. They are basic minions from the shadow realm who serve Enra. They don't have any powerful sides. They are not useless tho. These creatures always come in pack and they keep you busy/vulnerable to stronger demons. Always watch out for them, never let them surround you because this might make you die easily since you can't move anymore. If you encounter only crawlers, that would be easy but they are stronger when combined with other demons. Try killing them as quick as you can in large fights. They are pretty much vulnerable to every weapon or ki power so feel free to use anything against them. Katana is extremely effective against them since you can chop down their entire body. You can also use specialized katana attacks. If you want to use a firearm against them you can one shot them with shotgun. They are mobile so it's hard to land shots on them with other firearms except SMG. Slicing their torso sometimes drops a demon heart which could be collected to use as a weapon. Some of them can block your katana attacks(LMB) with their claws. Consider this while attacking them with your sword.
Enraged Bonus: They move extremely fast, has an charge attack and blocks most frontal attacks including bolts. Has more health and damage.

Armor: None
Hit Points: Lowest
Loot: None
Range: Melee(Explosion)
Speed: Low
Slashable Parts: None
Special Ability: Explodes when close. Spawns explosive balls. Stars rolling into you after a while.
Threat: 🟡 🟡 ⚫ ⚫ (low/medium)
Info: Mother demons are basic enemies. They are kamikazes. They run into you and go boom! Avoid getting close to them. You can shoot down the exploding balls of mothers spawn before they reach you. Prioritize rolling mother demons because they deal lethal damage on impact. Long ranged firearms are your friends. Remember, keep your distance and stay safe.
Enraged Bonus: They transfrom faster, spawn balls more often. Has more health and damage.

Armor: None
Hit Points: Medium
Loot: Demon Hearts(weapon)
Range: Melee & Ranged
Speed: Low
Slashable Parts: Arms, legs, torso, head
Special Ability: Can fly, shoots projectiles.
Threat: 🟡 🟡 ⚫ ⚫ (low/medium)
Info: Birdman isn't very tough but it deals decent damage by its projectiles. They usually come in packs so you better take cover or dodge rapidly during the fight to avoid getting shot by them. There are 2 types of them: walking(on ground) and flying(in air). Walking ones could attack you with their claws when you get close. Sometimes they charge a low ranged blast attack. Revolver and SMG are highly effective against flying ones, meanwhile katana is the best option for walking ones.
Enraged Bonus: They shoot more projectiles plus these projectiles are now explosive. Has more health and damage.

Armor: Medium
Hit Points: High
Loot: Demon Hearts(weapon)
Range: Melee & Ranged
Speed: Medium
Slashable Parts: Arm with shield, torso, head
Special Ability: Can send artillery like projectiles which stuns the player. Has a breakable shield.
Threat: 🟡 🟡 ⚫ ⚫ (medium)
Info: Trolls are the toughest lesser demons. They run around you in circles, shooting flame projectiles from their spears which stun you on impact. Firearms are mostly not worth to use against them due to their high hp and durable shields. I suggest you to use your katana and especially Divider of Heavens(charging pierce attack) and Wing of Crane(ranged attack). Both attacks go through their shields so you can easily kill them. They stop making the ranged stun attack after losing their shield but they act more aggresive.
Enraged Bonus: Has more health and damage.

Armor: None
Hit Points: High
Loot: Demon Hearts(weapon)
Range: Melee & Ranged(based on type)
Speed: High
Slashable Parts: Arms, legs, torso, head
Special Ability: Can become untargetable & invisible by stepping into shadow realm. Has a dash attack.
Threat: 🟠 🟠 🟠 ⚫ (high)
Info: There are 2 types of Warpers. First one has double swords. They disappear completely so you can't deal damage to them during it. They can also block your sword attacks with their swords. It's harder to land hits on their torso unless you are attacking them from behind because of their blocking swords. Try to stay mobile until you clear them all because their teleporting attack deals lethal damage, especially on harder gamemodes. You can slay them with katana or firearms based on your preference but katana is a more viable choice in harder gamemodes. Plus, if you combine your katana with your demonic powers(stun, water trap, heal etc.) you can take them out quickly. First, apply crowd control to them then charge your katana to perform Divider of Heavens attack. Doing this max 2-3 times even at hardest mode would get the job done. Avoid using explosives since they can teleport to in front of you, causing you to kill yourself. Demon hearts are very useful against them. Warpers usually attack in packs of 2-4 so even using one demon heart on them would reduce their number by %25 to %50 in most fights.
Second type of Warper uses a ranged attack which is throwing shurikens(sharp little stars). They can go invisible too but unlike the other Warper type, they are still vulnerable to any kind of damage. Burning them with flame thrower would be useful for spotting them when they are invisible. Another way to track them down is focusing on one Warper each time and following her until she is dead. You can see the shape of ranged Warpers during their invisible phase so try dealing damage to them while chasing them. They are less deadly than the other type of Warpers so it's not a big deal.
Enraged Bonus: Has more damage.


Armor: None
Hit Points: High
Loot: None
Range: Melee
Speed: Fast
Slashable Parts: None
Special Ability: Teleporting
Threat: 🟢 ⚫ ⚫ ⚫ (low
Info: Sometimes killing rabbits turn them into an hostile creature: a demon rabbit. They are always black with red eyes and there is an action soundtrack starts playing once a demon rabbit appears. They are able to teleport near you when you try getting away. Just walk backwards and spam bullets on them. They have high hp so be patient. If you want to avoid fighting them, then simply don't kill any rabbits.
Enraged Bonus: None

Armor: Extremely high(immune to damage)
Hit Points: High
Loot: None
Range: Melee
Speed: High
Slashable Parts: Back
Special Ability: Charge attack
Threat: 🔴 🔴 🔴 🔴 (high)
Info:Starts charging into you at high speed when you put a distance between you and him. He usually one shot kills you on insane and heroic game modes so you must dodge the charged attack no matter what! He is covered with thick skin so most of its body is immune to damage, except for the red glowing part on its back. You need to get behind him to kill him. Easiest way to doing that is letting him charge into you, dodging at last second before impact and getting him stunned. He gets stunned for few seconds when he charges into a wall. Using trees, corners, poles etc. to stop his charge attack is highly recommended for a safer fight. He is super annoying to deal with so try using charged crossbow bolts or rocket launcher to destroy them quickly after getting them stunned. You can also slay it with your katana by using the Divider of Heavens(charged attack), it goes through his body so you can deal damage to him even from front side by using that skill. It's hard to survive during it tho.
Enraged Bonus:

Armor: Low
Hit Points: High
Loot: Demon hearts
Range: Melee/Ranged
Speed: Low
Slashable Parts: Staff wielding arm, head
Special Ability: Summoning skeletons, raising dead demons, shield aura, AOE projectile, stun projectile
Threat: 🔴 🔴 🔴 🔴 (high)
Info: Shaman is extremely durable and powerful enemy. It can keep resurrecting fallen demons forever. You need to chop down its staff wielding arm to prevent them from resurrecting demons. Always aim for the staff wielding arm first. He creates a protective shield for few seconds after taking some amount of damage and spawns some burning skeletons. Just kill the skeletons and wait for the shield to end. Try dodging the stun projectile he fires from his wand because it stuns you on impact. Once you destroy the staff wielding arm, he starts sending waves of energy which is an AOE projectile. Try finishing them off quickly after destroying the first arm.
Enraged Bonus:

Armor: Low
Hit Points: High
Loot: Demon hearts, Warlord heads
Range: Melee/Ranged
Speed: Low
Slashable Parts: Arms, Head
Special Ability: AOE melee attack, ranged projectile attack, ranged hook, rage boost
Threat: 🔴 🔴 🔴 🔴 (high)
Info: This demon is a strong one but relatively less stronger than other great demons. It sends flame projectiles at long distance, dealing some damage. It also sends a gripling hook to grab you. It's not a big deal because you can dash away even after getting caught by the hook attack before he hits you with his weapon. Always focus on the head or arms for the fastest result. This demon empowers the nearby demons, causing them to get enraged. Having a Warlord alive in large scale battles might cause it to get all the lesser demons raged in few minutes. Try finishing it off as fast as you can. You can use its head as a weapon after slaying it only if you have unlocked the required skill for it.
Enraged Bonus:

Thank you for reading my guide! Hope it was hepful. You can add it to your favourites, give a like or even give an award if you feel like it. I spent a week by working few hours a day on this guide. Don't forget to write a comment. I will read your comments to improve the guide.

Have a nice day and enjoy showering in the blood of filthy demons!