Here is the full list of all 41 SCP: Containment Breach Multiplayer achievements.
Encountered the Peripheral Jumper.
Encountered a Recursive Room.
Found the cure.
Encountered an Old Cowbell.
Escaped the Old Man's Pocket Dimension.
Lured the Old Man through a Tesla gate.
Encountered the Old Man.
Encountered the Creatures with Many Voices.
Encountered the Builder Bear.
Encountered the Shy Guy.
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.
Found a Jaded Ring.
Encountered the Ghost.
Found a Blue Key.
Encountered an Old Coffin.
Encountered the Clockworks Machine.
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 the S-NAV Navigator Ultimate.
Acquired an Omni-level Keycard.
Didn't use console commands.
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.