The guide contains only achievements from the latest update of the game, look for the rest in other guides, there are enough of them already.

Bold text - the name of the achievement.
The underlined text - a description of the achievement.
Italics - my comments.


By the way, this is a translation of my original guide in Russian, so i probably made a few mistakes. Please, be patient!
https://steamproxy.net/sharedfiles/filedetails/?id=3359631749

In Ruins
Get the normal ending as every character.
Get the normal ending as every character.

Happily Ever After
Get the true ending as every character.
Get the true ending as every character.

Dirty Dawg
Stare at the shop screen for two minutes.
Stare at the Cordelia shop screen for two minutes.

Uh-Oh...
Trigger a Chunks mutation.
To get it, you need to play on the Painful difficulty or higher, or to go on looped run. Kill Chunks and he will start mutating, and you will get an achievement. The next time you meet, you will encounter one of two random mutations.

Unbound
Defeat Tentacles Chunks.
Defeat Tentacles Chunks. He will summon tentacles from the floor fnd throw them from himself, so keep your distance.

Nice Doggy
Defeat Dog Chunks.
Defeat Dog Chunks. You should meet him with pumped agility and/or with a bunch of speed items, since the mutated Chanks runs fast. The mousedog does not jump, so you can easily avoid him through jumping or flying.

Dreamer
Fall asleep.
You need to get to the second floor on a looped run. There you will find a room marked "ZZZ". As soon as the character enters and touches the bed, the achievement will be received.

Every Nook and Cranny
Explore the entire restored mansion.
Just visit every room, there are no enemies to fight.

Deep Sleeper
Clear the Dream.
Clear the Dream floor, same method as always.

Cracked
Destroy three eggs in one room before any of them hatch.
You can get this medal on the Dream floor. Explosions will greatly help you do thism or at least homing and penetrating projectiles. Almost always three eggs in one room spawn in the challenge room.

Soul Seeker
Clear the Mindscape.
Clear the Mindscape floor, same method as always.

Bone Meal
Destroy every part of a Bonefish before they disappear.
You can fight a Bonefish on the Mindscape floor. Destroy all enemies, then focus on a fish.

Survivor
Clear the Nightmare.
Clear the Nightmare floor, same method as always.

Swift Execution
Defeat all three hanging men within 10 seconds of each other.
Explosions, as always. Also Stethoscope would be a greate help.

Deathly Premonition
Reach the Leviathan
Clear all dream floors until you meet it.

Awakening
Defeat the Leviathan.
Usually it is a long fight, and boss spents half of it in the air. Any AoE damage is welcome!

Power Nap
Defeat the Leviathan's final form within 3 minutes.
All ways of strengthening and the possibility of indirect attack will help - the boss has turned into a flying worm and it is not at all easy to hit him.

Globetrotter
Complete a run where you visit all 4 main floors, all 4 alternate floors, the Shrine, and all 6 dream floors.
The strategy: in the first cycle, you need to go through the main and additional floors, like for the true ending, then jump off the balcony, walk to the second floor and visit the Shrine. If you dont have Sleeping Pills, go third cycle to the second floor and fall asleep. Dream floors are cleared as usual. Gladly, you can get the achievement on the easiest difficulty.

Glutton For Punishment
Clear an awakening ending run on X Must Die with all 12 general curses enabled.
I advise you to take a strong character, for example: Fuji, Digby, Boss with a bazooka. In this playthrough, maps will be very useful, because without them it will be very difficult to navigate the floor. It is advisable to clean the floors completely for the sake of money, which will not be enough, and learn how to kill a Chunks, because it appears very quickly.

Acolyte
Clear the Shrine.
The Shrine will open after receiving the awakening ending. It appears on the second floor.

Keen Observation
Damage a Tanuki before it drops its disguise.
Just shoot everything you see on the Shrine floor. Tanuki must not escape.

To play most of the new challenges you must unlock "Acolyte".

The Lifeguard
Complete No More Running.
All normal floors. This is the most difficult challenge. Jules and her shotgun are enhanced, of course, but the ability to move is tafen. All the heroine can do is jump and fly away from her shots. Apparently, the appearance of Chunks is disabled here, so you shouldn't worry about him. For a more or less convenient playthrough, you will have to take items for the firing range, increase the damage area, etc. The Jar Brain item is A MUST!!! With it, rooms and bosses will be cleared incredibly quickly, and you will have to constantly run shoot around yourself much less often.

The Fisherman
Complete Mental Power.
The dream route. This time Jeff has my favorite Jar Brain. It allows you not only to hit with 99.99% accuracy, but also to accumulate projectiles in the air, which is very convenient when fighting bosses, because you can shoot a couple dozen times before each one appears... In general, it goes through the first time, if you do not screw up.

The Sunbather 😍😍😍
Complete Triple Digits.
All normal floors. This challenge is not difficult in itself, but your mouse will fall apart by the end. You don't have to think too much about upgrades, because you only need to go through the main floors.

The Sailor Boy
Complete Time Attack.
All normal floors. Digby is given 8 minutes to complete this route and this is... enough! Just keep a combo and the guy will erase all living in the area in seconds.

The Sea Creature
Complete Death from Above.
The Shrine. Half of the enemies will not reach the Mumba if it hangs at the highest height, but you will have to run from some of them. Especially from the boss: set on fire - flew away, set on fire - flew away. Any items to enhance the fire - must have!

The Captain
Complete The Year of the High Roller.
The Shrine. This time Lydia is very limited in equipment - the pistol has only 50 rounds, and if she spends it all, she will die. There is nothing difficult in the test, if you find a good weapon in the box and do not miss most of the time.

The Swimmer
Complete Unarmed.
The Shrine. Luis is hysterical - his gun shoots very fast, but deals only one unit of damage. Clearing rooms with such meager damage is not an option, the test allows you to move immediately without killing anyone in the room. We search for all the treasures, collect good items and a set of "useless body parts" to create a force field that already causes good damage. Then - for the key and to the boss!

The Beach Bum
Complete Bulking Up.
All true ending floors. Fuji is not weakened in any way, so it is easy to play.

The Pirate Queen
Complete Weak Throw.
All true ending floors. The BOSS throws bombs right next to herself, but that shouldn't scare you. Are you afraid to get close? Lure the monsters to you and blow them up! Often, explosions will push enemies away from you, which will give you time for further action. You can think about upgrading agility.

The Model
Complete Ununundead.
All normal floors. Axel has been reset to 1 HP, but has gained incredible strength! It is unlikely that it will take more than one attempt to complete, because the character has a huge damage, fire rate, five rebirths.

Costume Party 3!
Unlock the D Costume for every character.
Unlock the D Costume for every character.

Darkness On The Edge Of Town
Get the awakening ending as Jules.
Get the awakening ending as Jules.

Man Of Constant Sorrow
Get the awakening ending as Jeff.
Get the awakening ending as Jeff.

Let's Find Each Other Tonight ♥♥♥
Get the awakening ending as Cordelia.
Get the awakening ending as Cordelia.

Time Passages
Get the awakening ending as Digby.
Get the awakening ending as Digby.

Waiting Around To Die
Get the awakening ending as Mumba.
Get the awakening ending as Mumba.

Blood On The Dance Floor
Get the awakening ending as Lydia.
Get the awakening ending as Lydia.

Falling Off The Face Of The Earth
Get the awakening ending as Luis.
Get the awakening ending as Luis.

One Hour Ahead Of The Posse
Get the awakening ending as Fuji.
Get the awakening ending as Fuji.

It's Gonna Be A Long Night
Get the awakening ending as BOSS.
Get the awakening ending as BOSS.

Don't You Worry About A Thing
Get the awakening ending as Axel.
Get the awakening ending as Axel.

Future Legend
Get the awakening ending as every character.
Get the awakening ending as every character.


Commencement
Unlock all medals associated with Jules.
Unlock all medals associated with Jules.

Road Warrior
Unlock all medals associated with Jeff.
Unlock all medals associated with Jeff.

Family Reunion ♡♡♡
Unlock all medals associated with Cordelia.
Unlock all medals associated with Cordelia.

Freshman Orientation
Unlock all medals associated with Digby.
Unlock all medals associated with Digby.

Lady's Man
Unlock all medals associated with Mumba.
Unlock all medals associated with Mumba.

Pay Day
Unlock all medals associated with Lydia.
Unlock all medals associated with Lydia.

Big Promotion
Unlock all medals associated with Luis.
Unlock all medals associated with Luis.

Fit As A Fiddle
Unlock all medals associated with Fuji.
Unlock all medals associated with Fuji.

The Bad Sleep Well
Unlock all medals associated with BOSS.
Unlock all medals associated with BOSS.

Big Kahuna
Unlock all medals associated with Axel.
Unlock all medals associated with Axel.

Fully Actualized
Unlock every medal associated with every character.
Unlock every medal associated with every character.

Milkbar Lads #1 Fan!
Unlock EVERY medal.
Unlock EVERY medal(not including the Goodnight) .

Goodnight
Thanks for playing!
After receiving 199 achievements, get the awakened ending once again.

So the guide has come to an end. I hope that, thanks to it, at least one person will not poke at random, as I did. If you need more detailed guides or help on other things, let me know :)
Thanks to everyone who read it!