On Eugene's ship, near the end of the game, you will have to face Eugene's tank form. Bring Pepper Box and Gre Nade along in your party, equip Pepper's "Bullet parts", have at least four Green Mosses or Cosmo Fruits, and be at least level 75 for each character. Use Pepper Box as the main attacker in the battle, with her "Pepper Flash" attack, Mag as the main healer attacker with his "Recovery and Hand parts", and use Gre Nade to give Pepper Box the Green Mosses or Cosmo Fruits after she uses "Pepper Flash". If Eugene is still alive and you run out of FP for Pepper and you have no more Green Mosses or Cosmo Fruits, use Mag to attack with "Magna Rave" attack and the battle should be over soon.
Use Mag as the main healer with Gre as the attacker with Lightning Spirit. Before doing that, use Mags Spray Parts to reduce the amount of FP for the attack. Also use Chain to attack. First, power him up with battle parts.
Have Mag, Pepper, and Gre. You must be at level 50 and Pepper must know Flat Shot. Have Mag and Gre attack while Pepper uses Flat Shot at least four times to lower damage and attack. Also have Mag be the healer most of the time, and have him use his strongest attacks.