Silent assassin requires 4 or more players on the server right? Because yesterday I got myself on a slapper fight with some dude and bitchslapped him to death enough times to win the round and the match. We were the only ones on the server.
EDIT- Come Hell or high water - be shot, slapped, stabbed, bludgeoned (if the props can actually hurt you), hit by an explosion (forgot the name for this...) on one life and survive.
This is perfectly doable, although it's difficult.