The President cannot pardon crimes from state charges.............
However, his power to pardon offenses against federal crimes is unlimited, which I think is perhaps the only such power in the Constitution. It’s never been dramatically abused, but the potential is there.
In a book I read recently, a wave of terrorism led Congress to pass a law giving jurisdiction over politically-inspired violence solely to the federal system.
The President promptly started pardoning anyone who killed one of his political enemies, giving him essentially the power to order executions at will. Entirely Constitutional, too.