I've been trying to get this achievement, and have gone through what I believe is every character and performed a fatality with each one, but the achievement has yet to unlock. I've gone into Nekropolis and viewed the stats on each player to confirm that each character has performed a fatality. I had been just playing the first match of beginner ladder, then performing the fatality for each character. Is there another, maybe unlockable player that I'm missing? Thanks.