Full list of all 12 Gotham City Impostors achievements worth 200 gamerscore. It takes around 40-50 hours to unlock all of the achievements on Xbox 360.
Earn 50 gold medals in Challenge mode.
Become a Nemesis 50 times.
Accept your first Promotion.
Kill 50 enemy players using the panic-slap melee attack.
Kill ‘em, fumigate ‘em, and pysch ‘em out… all over Gotham.
Complete all feats related to a particular gadget or support item.
Complete all feats related to a particular loadout weapon.
Earn a 10-kill streak.
Turn the tables in Fumigation when the enemy team's victory is imminent.
Unlock any locked loadout or costume item.
Finish one match of Gotham City Impostors.
Complete the Initiation mission.