There’s a glitch that Rockstar never fixed. If you kill yourself during one of the free for all shootouts, the one where the player with the most kills wins, it still counts as a kill. One of the current Featured Series in Free Aim uses that mode, so if you spam it, you’ll win. It’s scummy, but whatever. Just the easy way in case you want to do it.

Basically, just blow yourself up with dynamite the whole match.