The Beyonder is one of Marvel’s stronger beings and especially before the retcon. His powers were just about unstoppable for the heroes. That being said, he never faced someone quite like Goku. Goku’s speed will suffice for him to evade the Beyonder’s attacks and a good Kamehameha would get through his defenses. The Beyonder does well when he’s in control of the battle, but the tide will quickly shift once Goku starts to get serious. The Beyonder just won’t be able to dodge Goku’s unrelenting attacks. Goku wins.