[quote=@BrokenWashing]
If I were to use a pre-existing character, how mainstream would be ideal?

I'm asking because you've got characters like the Punisher who I think work for your setting but are generally well known.
[/quote]

Punisher wouldn't be accepted because of that very reason. Very well known. I am talking if you want to use original character go Bom Bom, Swamp Thing, the Chk'n Kao.