What is the opposite of a saint?

Sinner, broadly speaking. A heretic or demoniac or, in extreme cases, an antichrist would maybe qualify.

But the church doesn't make a big ceremony of cataloging and cannonizing the bad guys. You don't have priests running around looking for whatever the inverse of a miracle is in order to verify this or that individual was supernaturally evil. The closest might be the documentation of the subjects of exorcisms.

He ruins what others can’t.

The dogged insistence that Trump is a uniquely bad person (much less president) heavily neglects the long history of shit political leadership in this country's history. If anything, one could argue that Trump isn't an anomaly. The Post-FDR Era has been the anomaly. We've had an unusually good (relatively speaking) run of Presidents and now we're drifting back to the 19th century Tyler / Pierce / Buchanan / Johnson / Cleveland mean.

Americans had an unusually good run of luck following the Great Depression. And it propelled us into the Superpower sphere of influence. Now our luck has run out and we're plummeting back down to the baseline. Trump's a symptom and a vehicle of that decline. But he's got tens of thousands of fellow-travelers who have rallied behind him to drag the country down. We have an entire economic orthodoxy centered around the theory that Americans have had it too good for too long and they need to start living like their poverty-wracked Latin America / East Asia / Central Africa peers.