As for me personally, I say Kingpin.

Joker, Goblin, and Carnage are far more likely to cause chaos than even remotely care about taking control, leaving Black Mask, Fisk, and Ra’s.

Black Mask is a powerful and influential crime boss and leader, but nowhere near to the same extent as Ra’s, much less Fisk. It’s been proven that removing Fisk from the streets actually makes crime worse. And even when he’s in prison, he still controls the streets somehow.

This in turn leaves Ra’s, who easily gets second place. While he has the most experience out of everyone here, the fact he leads an organization of ninjas basically means he’d be in the shadows and wouldn’t really show himself to the public.

Also, out of Ra’s, Mask, and Fisk alone, while all three don’t have powers, Fisk literally physically fights deadlier people on a regular basis than the other two.

I'd say Fisk

Ah, but what about the possibility of there being no city to rule at all if Carnage ransacks it all by killing everyone and destroying everything (including his five opponents).

I know it's not a fight, but that seems like the most likely scenario which would make Carnage the winner by default.

Except I never said it was a singular city with all 6 trying to take control.

You said it was a neutral city and they have a month to take over THAT city. You never mentioned other cities, which would likely follow the same fate anyway.

I still think Fisk takes it cause again, Carnage wouldn't consider taking over the city. He doesn't give a damn about anything apart from murder and chaos.

I reiterate, Carnage causes chaos and destruction, murders whoever is in the city (which, more than likely, includes the other five) and, metaphorically, reduces it to rubble. There's no "city" to rule, only an empty mess. Carnage is the most likely of the six to do this (and potentially the only one of the six alive; if not, the others will move on to pastures anew anyway), which means he would win even if not meeting the win criteria.

That's the most likely scenario in my eyes, hence why I chose Carnage. There's an obvious loophole in the scenario you've presented, and I've exploited it.

Except I said “take over the city” not metaphorically reduce it to rubble.

I know you did, but Carnage is the type of character to reduce it to ruin, therefore wiping the city from the map and chasing the competition away. Carnage caused the mess, is the only person in whatever's left of the city and, as such, would be considered the ruler of that land by virtue of being the only one there.

You said it was a battle to rule the city, but you never specified HOW they could achieve that goal or whether the city still had to be functional. As I said, you've left, if by accident, a massive loophole to be exploited, I'm just smart enough to see and use it to my advantage.

Fair enough.