Has Another Player’s PC “ruined” the Tone of a Game for you?

[Mastikator]

Did the wizard/cleric character ever get their comeuppance in the form of being turned into a magic battery?

Also I dig the setting and might steal it.

Not yet. Maybe they won't. But I'll definitely say "I told you so" if I get the chance. I kinda suspect this is going to be a murder-hobo game.

Edit-

It is supremely irritating to me when a player just absolutely MUST play this one idea they had, regardless of how poorly it fits or any other circumstances, even if the idea isn't a joke (although it usually is) the total refusal to make concessions is a red flag to me.

IMO I totally agree. Bin the idea for another game, make it an NPC in your own game. For me character concepts are easy to come up with, especially in 5e where it's made easy, so just come up with something compatible with the game that is fun.