Who can beat him? In a straight up fight who would be bringing Goku down. Who could really put the hurt on Goku and even make him want to stop fighting, (which I dont think would ever happen. He loves it too much) Who is his Equal? Does he even have an equal? We know Goku is a master in Martial Arts. Some would say he is maybe the best.
You can choose anyone from any universe. Nobody From DB Universe! This is H2H only. They can only use their skills, power & speed, for example Superman could not use his heat vision, Goku could not use his Ki blasts, Darkseid could not use his OB. Now remember Goku is a Martial Arts master, you can put him up against someone stronger than him but it may not make a difference with his skill.