MTG

I'm at bracket 2-3, I'd say if you can kill a single player at turn5 with a great starting hand and luck, that's fast.

But it all depends on what your deck do, my most aggressive deck is doing damage to everyone (me too) each turn, stacking symmetric burn effects. It doesn't kill at early turns but it lowers everyone's HP low enough not to feel safe, denying them setup time and force to act, just to goad their whole board with my Kardur, and when only one opponent remains, do some fast finish, like Mob Rule.

Again, you might go slower if you have something nice to protect you from the most likely negative scenario. Say, Danitha theoretically could kill t4, but practically that's gonna happen way slower with an average luck, BUT lifelink vigilance is gonna keep your hitpoints high enough to have time - just get enough protective gear so you don't lose her too often.

You can see all the decks mentioned here.