Amber Diceless which compares stats with GM fiet based on the situation.
Everway which also compares stats but if things are close has the GM interpret a picture card.
DramaSystem which is designed for PvP play and trades tokens for conceding a scene (and multiple tokens can be spent to force another player to conced).
Fiasco which does use dice, but not (as random number generators) to determine outcomes. A player, on their turn, can choose to establish a scene or hand that responsibility off to the rest of the group. Whoever doesn’t do that picks if the outcome of the scene is good or bad for that player’s character (subject to the availability of good or bad tokens in the pool). Second editor ditches the dice entirely and adds cards instead, I haven’t played that version.
For the Queen isn’t a traditional RPG. It provides a card deck that asks questions about characters. Figuring out the answers lets everyone learn about all the characters (including their own).
I’m not really familiar with RE9, but a some surface level research suggests that (mechanically speaking) mutation is just “the abilities of bad guys change mid-fight”.
That seems like it is easy enough to bolt onto more-or-less any game.
You just need a variant stat-block for the enemy and something to trigger it.
D&D 5.5 has a bunch of monsters with abilities which change when they are on half hit points but you can use other triggers such as “is the target is a spell” or “the GM decides the players are having too easy a time and spends a Fear point”.
The trick is to come up with mutations and associated mechanics which fit the narrative.