The loser writes an original, sincere poem about their fantasy season and performs it at a coffee-shop open mic with zero irony allowed. Snapping is permitted; laughing is not. The text of the poem is archived in the league constitution forever.
Budget note: this one costs nothing but dignity, which makes it a strong pick for leagues that would rather spend the pot on the champion than on the loser's downfall.
Seen in the wild: scoutcast.ai