Here is the full list of all 28 Forsaken Remastered achievements.
Defeat Cerbero
Defeat Beard
Defeat LA Jay
Defeat Ex Cop
Defeat Rex Hardy
Defeat Foetoid
Defeat Nim Soo
Defeat Nutta
Defeat Sceptre
Defeat Jo
Defeat Cuvel Clark
Defeat HK5
Defeat Nubia
Defeat Lokasenna
Defeat Mofisto
Defeat Slick
Defeat Flygirl
Max out on orbital pulsars
Discover all secret areas in a single player campaign
Collect all crystals in a single player campaign
Complete single player mission 'Fishy' on Total Mayhem without losing a life
Defeat the Fleshmorph
Unlock all playable characters
Defeat the Avatar
Defeat the Exogenon
Defeat the Ramqan
Defeat the Maldroid
Unlock and complete all bonus levels in the single player campaign