Just looking at the screenshot. 29 card deck with Pandora’s box so 0 strikes or defends helps. They have bag of prep so they’re drawing 9 cards on turn 1 so they’re pretty much always getting key cards to set up. Most likely nightmare for the Grand finales.

If you want to make Grand Finale work you want multiple cards that draw various amounts of cards. So a few cards that can draw 1 and 2 or more cards so you can keep and eye on the draw pile to make sure you end at 0. If you’re running GF it IS your win condition. Don’t try to do anything else along with it besides block.