Here is the full list of all 16 8-Bit Commando achievements.
Complete every mission on hard difficulty
Complete the seventh mission
Complete at least one versus match
Complete a mission without dying or losing any health
Collect every type of powerup
Complete the sixth mission
Complete the fifth mission
Complete any mission in coop
Complete any mission in under 2 minutes
Complete the fourth mission
Take out 81 bad guys
Complete the third mission
Complete the second mission
Fire over 666 bullets
Complete the first mission