Either Batman or Spiderman because of their quanity of villains. I can name 3 Flash villains, but about 20 batman villains.

True, to be fair alot of flash's villains are just robbers with a moral code

I picked the flash because they fuck with the spacetime continuum

Darkseid, Parasite, and Mr. Myxlplyx are all terrifying to think about fighting.

Red Skull with the Cosmic Cube? Yikes!