Final Gambit (いのちがけ Extreme Risk) is a Fighting-type move introduced in Generation V. The user deals a life risking attack and faints, and the opponent receives damage equal to the user's lost HP. If this move misses, the user doesn't faint.
Despite being a Fighting-type move, only three fighting types can learn it.
If Victini were to use Final Gambit at level 100 with a positive nature that raises HP and have 31 IV's in HP, then it could deal 404 damage: the highest possible damage that a Pokémon that can learn this move by leveling-up could do. The Fighting-type that could attack with the highest amount of damage with a nature that raises HP and have 31 IV's in HP would be Lucario at 344 HP (Lucario could learn Final Gambit as a Riolu if it evolves after level 55).