Final Showdown is a mythic Instant card from Outlaws of Thunder Junction (OTJ), collector number 11. Current market price: $5.51 (foil $5.73), TCGplayer market prices via Scryfall.
Spree (Choose one or more additional costs.) + {1} — All creatures lose all abilities until end of turn. + {1} — Choose a creature you control. It gains indestructible until end of turn. + {3}{W}{W} — Destroy all creatures.