if you read marvelman who wins this fight

Probably Prime. He has thrown down with multiple Kryptonians and multiple Corps at the same time. He has had basically armies of heroes attack him to try and get him down. Would be a cool fight and would leave wherever they fight in absolute ruins.

Kid Marvelman is not in the same league as SBP. In the early history of Marvelman, we see the British government attempt to kill Marvelman, Kid Marvelman and Young Marvelman. Close proximity to a small nuclear detonation is sufficient to kill Young Marvelman. Despite Kid Marvelman being more powerful when he is older, his power level is but a fraction of SBP. To put that in perspective, has survived energy blasts capable of destroying continents and even planets.

Superboy Prime