100% Completion

In total, there are 48 achievements in the game, of which, for the most part, this is the discovery of a particular character. Achievements related to warp-zones (warp-zone) and patches (bandages). Achievements for the passage of light and dark worlds. And secret achievements.

I recommend checking out this guide:
https://steamcommunity.com/sharedfiles/filedetails/?id=2851952830

There are 16 characters in total in the game. They open when you collect a certain number of plasters, after passing through special warp zones, as well as when entering secret codes. The Commander
- unlock CommanderVideo character (complete warp zone 1-12) The Bootlicker
- unlock character Jill (complete warp zone 2-8) The jump man
- unlock Ogmo character (complete warp zone 3-16) The Flyguy
- unlock Flywrench character (complete warp zone 4-18) The Kid
- unlock The Kid character (complete warp zone 5-7) I Have Crabs!
- Unlock The Head Crab character (collect 10 patches) Metal Head
- Unlock character Josef (The Machinarium Robot) (collect 30 patches, also unlock character Alien Hominid) I Smell something Fishy...
- unlock character Naija (collect 50 patches) MS PAINT RULZ!
- Unlock the RunMan character (collect 70 patches) Vx6
- unlock Captain Viridian character (collect 90 patches) Accidental Arsonist
- unlock character Mr. Minecraft (Collect 100 Band-Aids)

As the game progresses, you may see a strange portal that looks like a black hole. This is the warp zone. Some of them are visible immediately, "with the naked eye". And some can only be found by "combing" the map, well, or randomly.

Warp zones are divided into 2 types:
Retro warp zones
Warp zones with a character

To get the 4 achievements that will be shown below, you only need to complete the retro warp zones.

Nostalgia
- find one warp zone (not necessary to go through) Living in the Past
- complete 5 warp zones old school
- complete 10 warp zones Retro Rampage
- complete all warp zones

Each chapter has one special level (glitch, game crash), after passing which an achievement is given. To get to the glitched level, you must first beat the boss in this chapter, then choose the easiest level (mostly always the first) and go through it (15-20 times) until Bandage Girl starts to glitch (you will know this by the visual effect and special sound). In order for the achievements to open, you must complete these levels. If you die, then you can go to these buggy levels by the yellow marker to the left of the 1st level of this world.

N#7*<1!23
- secret achievement (complete a buggy level in The Forest chapter) &*>?1$
- secret achievement (complete a buggy level in The Hospital chapter) (=+66&1$
- secret achievement (complete a buggy level in The Salt Factory chapter) ^**5%_=+12
- Secret Achievement (Complete a buggy level in The Hell Chapter) *|-0&&
- secret achievement (complete a buggy level in The Rapture chapter) N&8^2^%$1``
- secret achievement (complete a buggy level in The End chapter)

Video with the passage of all buggy levels:
https://youtu.be/IIQRwVTbOmY

To get these achievements, you need to complete the levels in the light and dark worlds as quickly as possible. The main condition is that all levels of the chapters must be completed on A + and the boss has been completed.

Rare
– secret achievement (complete all levels of both the light and dark worlds of The Forest chapter in total in a minimum time of 265 seconds or less; warp zones, buggy level and boss do not count) Medium Rare
– secret achievement (complete all levels of both the light and dark worlds of The Hospital in a total of 445 seconds or less in total; warp zones, buggy level and boss do not count)

Medium

– secret achievement (complete all levels of both the light and dark worlds of The Salt Factory chapter in total in the minimum time - 515 seconds or less; warp zones, buggy level and boss do not count) Medium Well
– secret achievement (complete all levels of both the light and dark worlds of The Hell chapter in total in the minimum time - 500 seconds or less; warp zones, buggy level and boss do not count) well done
– secret achievement (complete all levels of both the light and dark worlds of The Rapture chapter in total in the minimum time - 688 seconds or less; warp zones, buggy level and boss do not count)

To get these achievements, you need to go through the light or dark world (at your discretion) in one go, never dying. The order of completing the levels is not important, so you can go through the difficult levels first, and then those that are simpler. There is no need to go through the boss in the bright world. You can pass any character except Mr. Minecraft and Meat Ninja.

If you have a good reaction, then at critical moments (right before death, for example) you can pause and change the character (the level will start again, but the achievement will not be reset).

Light Worlds:
wood boy
- Complete the bright world of The Forest Chapter without dying Needle Boy
- complete the bright world of The Hospital chapter without dying Salt boy
- Complete the bright world of The Salt Factory chapter without dying Brimstone Boy
- complete the bright world of The Hell chapter without dying Maggot boy
- complete the bright world of The Rapture chapter without dying dead boy
- Complete the bright world of The End chapter without dying girl boy
- Complete the bright world of The Cotton Alley Chapter without dying Dark Worlds:
Squirrel Boy
- Complete the dark world of The Forest Chapter without dying Blood Clot Boy
- complete the dark world of The Hospital without dying missile boy
- Complete the dark world of The Salt Factory chapter without dying Demon boy
- complete the dark world of The Hell chapter without dying Zombie Boy
- Complete the dark world of The Rapture chapter without dying Dr. Fetus Boy
- complete the dark world of The End chapter without dying Impossible Boy
- Complete the dark world of The Cotton Alley Chapter without dying

Achievements that give after completing the game and completing 100%.

The End
- defeat Dr. Fetus in the bright world The Real End
- defeat Dr. Fetus in the dark world Suffragette
- complete Cotton Alley in the bright world Seneca Falls
– complete Cotton Alley in the dark world golden god
- Finish the game in 100% (complete all levels and warp zones of all chapters except The Cotton Alley on A+ (buggy levels do not count towards this achievement) and find all plasters; completing 100% also unlocks Meat Ninja)

These achievements can be obtained at any time.

The Kid's Xmas!
- complete one level of the chapter "The Kids Xmas" in Super Meat World The Golden Gift!
- complete all levels of the "The Kid's Xmas" chapter in Super Meat World in one go (without exiting the main menu of the game) Video with the passage of the chapter "The Kid's Xmas": =D
https://www.youtube.com/watch?v=yVvFRk_F4aM
Well look at you!
- secret achievement (enter the petaphile code on the character selection screen and after you hear the phrase “PUSH DA BUTTONS”, select the Super Meat Boy character; after appearing in the level, you will receive an achievement and play as Tofu Boy until you change character or exit the level)

Other secret characters and how to unlock them:
Brownie - enter the code RB, RB, RB, B, B, B, X on the character selection screen using the XBOX-360 controller (did not try it on the keyboard, it can and is possible) and select the Super Meat Boy character (note: the code will only work if you cleared the boss in The Salt Factory chapter)
Goo - enter the gooball code on the character selection screen and select the Super Meat Boy character
Tim - enter the outtatime code on the character selection screen and select the Super Meat Boy character (there will be no “PUSH DA BUTTONS” phrase)

Thank you for your attention!!! Rate, comment, ask questions if something is not clear. And have a nice game)