Cinder (Killer Instinct) vs Portgas D. Ace (One Piece). If you have a UniVS template with a picture of the two to replace the pictures, feel free. Comment your opinion on who would win and if you'd like to see this as an episode.
These two are made of fire, being able to deconstruct their solid bodies to use as a weapon. They are criminals, Ace being a pirate, and Cinder being a convict. Also, in their stories, they are currently dead, having been killed by a similar element user.
These two actually don't show a lot of impressive feats on their own and require scaling. They can both potentially be immune to physical hits and could potentially be burned. The deciding factor here might be who can get hotter, faster. This goes to Ace, in one of the strongest feats in One Piece, Ace was able to stop all snowfall on almost the entirety of Drum Island just by him being there. This would put the amount of heat energy Ace puts out in the megatons. This is one fire fight Ace is going to win.