Deal With The Devil
Event
Cost: $0
+1 Buy
+$1
Discard the top card of your deck. The player to your left chooses whether you trash it or gain a copy of it.
1. Be first player
2. Buy this a million times
3. Buy the supply
4. Win
Events must be bought. 1-1+1 = 1 Buy. Step 3 fails to happen.
You could add in Travelling Fair though.
Travelling Fair takes away the excess $1, so that doesn't work either.
You still get a guaranteed Province every turn, and
if your opponent keeps insisting you get copies of things, you'll run two piles in Coppers and Estates, while still getting the Province. However, that is the best scenario for P2, which is still brutal because you only need to play Deal w/ the Devil as many times as you need for Province on subsequent turns, not an infinite number of times, thus making a Province hit unlikely.
If P2 chooses to trash all the cards, you can simply get 5 Provinces without retribution of trashing, as they would be in your hand. After that, you simply get 8 Provinces in 8 turns. Brutal.
And Traveling Fair DOES work. It's too OP.