Here is the full list of all 41 SCP: Containment Breach Multiplayer achievements.
Encountered the Shy Guy.
Escaped the Old Man's Pocket Dimension.
Found the cure.
Encountered the Peripheral Jumper.
Encountered the Old Man.
Encountered the Builder Bear.
First played the multiplayer.
Encountered the Zombie Plague.
Encountered the Bad Composition.
Encountered the Possessive Mask.
Recontained SCP-055.
Encountered the Old AI.
Acquired the "Telekill Alloy".
Encountered the Shadow Lamps.
Obtained a liquid from the Coffee Machine.
Used SCP-420.
Found and equipped the "Lovecraftian Locket".
Swallowed a sample of Panacea.
Encountered an Old Cowbell.
Found a Jaded Ring.
Encountered the Ghost.
Found a Blue Key.
Encountered an Old Coffin.
Encountered the Clockworks Machine.
Encountered the Creatures with Many Voices.
Encountered the Sleep Entities.
Encountered a Recursive Room.
Read the Encyclopedia of Common Diseases.
Encountered the Atrocity Skull.
Entered Doctor Maynard's office.
Entered Doctor Harp's office.
Acquired the S-NAV Navigator Ultimate.
Acquired an Omni-level Keycard.
Didn't use console commands.
Lured the Old Man through a Tesla gate.
Encountered the Hole In The Wall.
Wore a GP-5 Gas Mask.
Beat the game on Keter difficulty.
Escaped the facility in breach mode.
Became MTF in breach mode.
Became scientist in breach mode.