Munchkin: Quacked Quest

Add a 2nd player with a 2nd controller, and play through the dungeon until you reach a room with a pit. Move the 2nd player to stand right next to the pit, then with your main controller hit them so they are knocked back into the pit. The 2nd player will respawn as a ghost, simply move them back into the same place as before, rinse and repeat.

Edit: The below note has been confirmed to work by Logans Old Man. Apparently you just need to set them up, knock them in once, and let the respawn deaths rack up to 25.

NOTE: It's possible that you may be able to knock them in once, let them respawn without moving them, in which case they will immediately fall into the pit again. Let this happen 25 times over and over and it could count all of them as the 1st player pushing them in 25 times. (I let this happen 3 times before starting to move them back to the ledge after spawning, and by my count I only actually pushed them in 22 times, so I think this way may work, but can't confirm.)