Berserker - Kill people with an axe or tomahawk. Load up "Welcome to Hope", there is an axe next to the bar on the left of it, on a dart board. Just pick it up and kill everyone with it.
Brutus - Kill people with a knife, most missions have a knife.
Spook - Kill people with silenced pistol. Sneak up behind people, and press X with your Silverballers out. So you grab them and shoot them.
Glass Cannon - Kill people with a shotgun. Load up "Welcome to Hope" again, go into the toilet, and into the vent. Go through the vent, and the room on the other side will have a shotgun in it. Pick it up and unload on the crowd.
Bank Robber - Take people hostage. Load up "King of Chinatown", find an area with no cops, and just use "Human Shield" on civilians. Just knock one out and pick up another one.
Pitcher - Kill people 5/6 people with a throwing knife, and don't get spotted. So load up Library on Run for Your Life, you should have a knife on you. Just take out the cops and hide them, going the left-side is best for this.
If you do not have the knife on you, start from the beginning of Run for your Life and do it.