Just imagine if a President's power to pardon is absolute, as Orange Buffoon says...

even to the point of pardoning himself.

I don't think you'll have to guess what that amounts to.... a dictatorship.

Don't like a particular political rival? Have him killed... you won't even have to be secretive about it... just pardon yourself and even brag about it if you like. And stay in office, too, while you're at it because if you threaten enough people with the same fate they probably won't have the stomach to impeach you.

Just what James Madison would have wanted!