Hunting Grounds and Donate (and a +buy source otherwise it's difficult)
When trashed Hunting Grounds gives you either a Duchy or three Estates.
The trick is to have two piles empty and then buy Donate to trash all your Hunting Grounds and using the gains to either empty the Estate or Duchy pile. You will get 3VP per Hunting Grounds (unless you need to gain 1 or 2 Estates to empty the pile), plus all the VP gained during your turn (where you can still use your Hunting Grounds).
Because the endgame state is checked after your turn but before you Donate your opponent gets a last turn. But they cannot use Donate to trash Hunting Grounds as the game will finish after their turn.
So in this game, I bought two Provinces and made sure two piles were empty. And with the last remaining buy I bought Donate.
With Donate I trashed my four Hunting Grounds, gaining a Duchy and 8 Estates. Thus so emptying the third pile. (23VP)
The opponent would have to been able to buy 4 Provinces (24VP) to get ahead of me which she wasn't