1. Darkseid
This is less a question of whether or not a human could beat Darkseid (R.I.P. Dan Turpin), than a question of who would win in a fight between Darkseid and Doomsday.
Because that’s essentially what Brock Lesnar is at this point: a destroyer, not of worlds but of gods. And that’s a pretty good place to be in the WWE Universe.