Wild Arms - Boomerang Flash

The requirements to unlock this would be claiming the Boomerang after he bites the dust and having cleared the arena. Once you have both done (order up to you), you can take on this opponent for Rudy's ultimate weapon.

The annoying part here is the chance of instant death. If not for that, this fight would be fairly easy for how late in the game it unlocks. The strategy is roughly the same for everything from here: Cecilia debuffs the enemy then starts healing while Jack spams Magnum Fang and Rudy spams Phaser. When the force gauges fill up, we have some other options, but we only get those if the instant kill does not instantly kill...