Here is the full list of all 41 SCP: Containment Breach Multiplayer achievements.
Encountered the Zombie Plague.
Encountered the Creatures with Many Voices.
Encountered a Recursive Room.
Encountered the Shy Guy.
Encountered an Old Coffin.
Encountered the Shadow Lamps.
Found the cure.
Acquired the "Telekill Alloy".
Used SCP-420.
Read the Encyclopedia of Common Diseases.
Wore a GP-5 Gas Mask.
Encountered an Old Cowbell.
Found a Jaded Ring.
Found a Blue Key.
Encountered the Clockworks Machine.
Encountered the Old Man.
Encountered the Hole In The Wall.
Encountered the Peripheral Jumper.
Encountered the Builder Bear.
Escaped the Old Man's Pocket Dimension.
First played the multiplayer.
Encountered the Bad Composition.
Encountered the Possessive Mask.
Recontained SCP-055.
Encountered the Old AI.
Obtained a liquid from the Coffee Machine.
Found and equipped the "Lovecraftian Locket".
Swallowed a sample of Panacea.
Encountered the Ghost.
Encountered the Sleep Entities.
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.
Beat the game on Keter difficulty.
Escaped the facility in breach mode.
Became MTF in breach mode.
Became scientist in breach mode.