Alright, this is an insane theory based on the themeing of the game, and I could be way off, but so far, my speculation goes hand in hand with that big ol' chart up there.
I double check the AGDQ website that Stefl linked and when looking up games I noticed something strange. There were many games listed as Any%, and a few listed with specific goals for the speedrun.
Now I crosschecked this with every game claim so far.
Any%
Prof - Timecop
linkz - Psychonauts
Trucks - Bishi Bashi Special
Arm - The Addams Family
Clyde - New Super Hook Girl
Zero - Furi
Miz - FE: Blazing Sword
Blade - MN9
Spurge - Trauma Center: New Blood
Specific Goals
FF - Undertale
Noct - Mega Man
Axumdouche - Hyper Princess Pitch
Sword - Hitman: Blood Money
Hat - Super Smash Bros. Melee
This leads me to think, maybe, just maybe, the mafia are the ones with specific goals attached to them. This checks out with Clyde's claim that Hat is lying, and if he was, Sword and Axum being scum here would fall in line with the specific goals theory, because that makes all three lying mafia scum douche bags.
So Noct and FF would be the final two remaining mafia members. I'm led to believe that Noctis was the one who plundered Arm's body.
This is just a theory, mind you, but it pieces together oddly well with all the information provided.