Welcome to Achievement guide for 100% completionist. First of all I'm sorry if there is any mistake in text. English is not my main language.

Genesis has a lot of pretty easy achievements that mainly require exploring, but some of them are also a little bit tricky because of camera angles. Game also has 2 difficulty releated achiv, but u can finish those after main story. Everything can be done on 1 save and you can start on any difficulty.

Mammon
Defeat Mammon Lord of Hell.
Story related, cannot be missed.

Belial
Defeat Belial Lord of Hell.
Story related, cannot be missed.

Astarte
Defeat Astarte Fallen Angel.
Story related, cannot be missed.

Dagon
Defeat Dagon Lord of Hell.
Story related, cannot be missed.

Moloch
Defeat Moloch Lord of Hell.
Story related, cannot be missed.

You can find side quests in every mission and some of them are actually counted as achievements.

Soul Cache
Destroy all 4 Soul Caches in The Slag Pit.
Can be found in Mission 2

Hell's Forge
Gather all the ingots in the Inferno Vault and take them to Hell's Forge.
Can be found in Mission 3

Close the Rift
Close the rift leaking void creatures in Icebind Cavern.
Can be found in Mission 4

Respect For Animals
Defeat less than 5 hounds before killing the Houndmaster in The Horde.
Can be found in Mission 5

The Dead Court
Defeat the Dread Lord's subjects in Decay.
Can be found in Mission 7

Why'd It Have to Be Snakes?
Defeat every snake in Decay.
Can be found in Mission 7

Good Deeds
Save the uncorrupted angels in Bastion's Fall
Can be found in Mission 11

Infested
Defeat the grub queen in The Maelstrom.
Can be found in Mission 12

Demolition Derby
Destroy 10 structures in War Machine.
Can be found in Mission 15

Ready to Blow
Destroy all 12 of Moloch's supply caches in War Machine.
Can be found in Mission 15

Blademaster
Defeat Moloch without taking damage.
Can be found in Mission 16

I recommend you to first find a map in chapter. It's usually right in your way. After revealing every item, you can start collecting them.

Mint I
Collect 50 Boatman Coins.
Self explanatory

Mint II
Collect 200 Boatman Coins.
Self explanatory

Mint III
Collect 350 Boatman Coins.
Self explanatory

Garden of Forking Paths
Collect every Boatman Coin in the Boatman's Labyrinth.
You can find guide posted on steam explaining all requirements.

Master of War
Learn all 3 of War's Wrath abilities.
One is obtained by default, other 2 can be found in chapter 5 and 8 in Epic Chests

Master of Strife
Learn all 3 of Strife's Wrath abilities.
One is obtained by default, other 2 can be found in chapter 3 and 5 in Epic Chests

A Bullet for All Seasons
Find all 5 of Strife's elemental ammo types.
2 of them are sold by Vulgrim after a few chapters and others are found in chapter 2, 5 and 12

Walking Armory
Find all 5 of War's elemental enhancements.
2 of them are sold by Vulgrim after a few chapters and others are found in chapter 4, 7 and 11

Gatekeeper
Unlock every Trickster Door.
Trickster Door can be found in almost every Chapter.
Last Door:










Collector
Collect every type of creature core.
Can be obtained after finishing story and progressing through lv.21 arena. It also requires finishing first stage of Leviatan's Landing

Full of Hell
Complete all 17 levels on Hard difficulty.
Difficulty can by changed any time which means that you can re-run all chapters again.
Last Chapter is Boss fight with Wicked K in Void

The Promised End
Complete all 17 levels on Apocalyptic difficulty.
Difficulty can by changed any time which means that you can re-run all chapters again.
I recommend to raise your power level to 1500 before replaying on Apocalyptic

Are You Not Entertained?
Achieve a score of 70000 or higher in the arena.
Can be obtained after completing story and unlocking Endless arena. All you have to do is obtain 70 000 points and leave arena.

Wicked Killington
Face the Trickster himself Wicked Killington.
First you need to complete Gatekeeper, only after that you can enter Trickster's arena. Defeat him and achievement is yours.

Good luck in collecting achievements. I hope this guide helped you a little bit, if yes then you can give it a thumbs up so everybody can see how to collect everything.

I took inspiration from The Horror Network.
All videos added in this guide are made by someone else.
Videos are from KyKiske7 & goodgamez.