If he punched him in the nuts Brock would pull out his hunting rifle and just end the whole thing. In all seriousness: If we're just talking about a spy vs spy game of who can one-up the other as far as eye gouges and nut punches go, then no technique really matters at all. I'm assume that Tyson will not chew his way through BLs arm and then take it home with him, and I'm assuming that Brock will not attempt to put both his thumbs through MT's eye sockets, bad 60s kung fu style. If that's the game, then pick whatever ending you want. Anything is possible. If we're talking about the skillset Lesnar has an an MMA fighter against the skillset Tyson has as a boxer, give me Lesnar all day long.