Here is the full list of all 12 B99 achievements.
B99 Defeated
B99? Defeated
SAIBAONI Defeated
UNAGI Defeated
GANKYASSURU Defeated
REZAROBOTTO 3 Variants Defeated
GANKUREIJI 3 Variants Defeated
Omega Combat Sim Unlocked
Gamma Combat Sim Unlocked
Beta Combat Sim Unlocked
Alpha Combat Sim Unlocked
BUROKKO HEDDO-SAN 3 Variants Defeated