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