This is not so obvious to me. I don't think the evidence supports your claim that its "major use is corruption." The vast majority of pardons seem to be entirely unrelated to corruption.

However much you may dislike the particular individuals that trump has pardoned, he has used the pardon in a much more restrained way than Obama, who gave an order of magnitude more. So far, the pardon power is still a net good.

Okay, but why should the President be able to pardon people close to him including himself? Shouldn't the power be circumscribed to things that aren't obvious corruption? GWB pardoned Scooter Libby. George HWB pardoned Iran-Contra conspirators. Ford pardoned Nixon.

Maybe, what would such a law look like?

You could start by forbidding pardons to members of presidential administrations for offenses incurred during their term. You could also make "crimes against humanity" ineligible as well which would forbid the pardons of the Blackwater contractors that massacred Iraqi civilians.

Trump has pardoned far fewer people, but for the same reason the ratio of compassionate to corrupt pardons under Trump is much worse. Dozens of Trump's pardons had some direct benefit to him or his cronies. And among modern presidents he has pardoned strikingly few people.

I am not aware of any corrupt pardons under Obama similar to that of Marc Rich under Clinton, much less more egregiously corrupt pardons like that of Ford by Nixon or Manafort by Trump.