Here is the full list of all 21 Sacrifice Your Friends achievements.
Complete all missions in the Nameless City
Complete all missions in Innsmouth
Play a conquest
Complete the first mission
Play a deathmatch
Complete all missions in Innsmouth with a gold rating
Complete all missions in the Nameless City with a gold rating
Complete all missions in the Miskatonic Valley
Complete all missions in the Miskatonic Valley with a gold rating
Complete all missions in all stories with a gold rating
Complete any mission with a platinum rating
Complete all missions in any stories with a platinum rating
Complete all missions in all stories with a platinum rating
Play a game online
Unlock and play a multiplayer game in every arenas
Play a tournament
Play all tournaments
Create and play a custom tournament
Reach profile level 10
Reach profile level 20
Reach profile level 30