As a Boss
Leon and the Mech share the exact same abilities, as such, the following description applies to both bosses.
The boss will only use three abilities during this battle: Aerial Cruiser, Field Inducer, and Plasma Shower. Aerial Cruiser and Field Inducer aren't very threatening on their own, and the boss will chain copies of these attacks throughout the battle. The two attacks will eat away at the party's HP, though armor with Life Protection will keep the party safe from any real damage.
Plasma Shower is the only attack in it's arsenal that can cause any problems, as it deals high HP damage, hits all characters on-screen, and has a moderate chance of inflicting Paralysis. Luckily, the boss uses this technique rarely. Good equipment and low character Weight make this fight manageable.
Starter: "I won't allow anyone to interfere. Not Father; And certainly not you....Brother!"
Defeat: "K-Kurt! Help! Something's.....swallowing....me!"
For all the lines of the character, go here:
Field Inducer has two unique animations, for reasons unknown. The alternate version has no additional effects, rendering it pointless. It may have been part of an attack that was cut out of the boss's repetoire; though one can only speculate.