Bugs Bunny. Gag characters always beats serious characters, except in rare circumstances where the gag characters lose their gag powers and can't counter serious character attacks (because it's making fun of the gag character). read more
Depends on the universe rules that fight happens under. If the Toon Force is present Bug Bunny wins versus just about everything in the DC universe in that case. read more
But that's not super restrained Mxy that's on par with toonforce or who fights Supes so you can't really compare. The actual comparison for this is near unlimited very short range reality warping with the ability to use the fourth wall as an exit, Bugs should win just because Superman lacks a meaningful counter to Bugs' reality warping stuff. read more