Refocus you're attention. The problem is not with the pardon power. You said:
> That bad actor is Trump. But the warnings from abusing these limitations
But that's the thing, the pardon power is not supposed to be limited. How would you limit it? Who would actually tell the President "No" and on what authority? The obvious choices are Congress and the Courts but they already checks to balance the the President. That's why they can't check it -- the pardon power is the President's check on them (along with the veto power).
Hamilton said:
"Without an easy access to exceptions in favor of unfortunate guilt, justice would wear a countenance too sanguinary and cruel."
That's what it's for. After all the process, if justice is not done, and there's no way to undo it, then justice will not survive and there will be no confidence in the system. But with great power comes great responsibility, so you need someone very responsible in that position or else it doesn't work.So then how do we fix it if not by adding laws and rules? We don't elect people like Trump, who think they are above the law. That's it. I know it seems kind of glib but it's not a high bar to just avoid malignant narcissists.
The reason Trump is abusing the pardon power is because he does not consider what he's doing an abuse. He sees that he has the "right" to do it under the Constitution, and to him, anything he has the right to do, he can do. And you know what, despite him being abusive he does have the right. But that's the thing, we gave him that right, and we can take it away and give it to someone else who won't abuse it.
That is the actual check on the pardon power, but that's on us. It's on us because Trump abused the pardon power in his first term by dangling pardons in front of Paul Manafort when he was being investigated by the DOJ, so none of this should be a surprise to anyone. Obama's "abuses" and Bidens "abuses" are on everyone's lips here, but not a single word for Trump's 1st term abuses (mine is the first mention of the Manafort pardon in over 1000 comments). So if you really want the root cause of his power abuse beyond his psychopathology, it's that -- because not only did we not care he did that, we actually reelected him as he promised to abuse his power during the campaign, so why wouldn't he actually do it?