Recommended Team: Sonic (Leader) & Tails (Partner) - Super Sonic transformation required.
The Ultimate Gizoid, also known as G-Merl in its powered-up form, is the true final boss of Sonic Advance 3. This fight is only accessible if you have collected all seven Chaos Emeralds. Sonic will transform into Super Sonic for this battle, making him invulnerable and significantly faster, but his ring count will constantly deplete. If your rings reach zero, you revert to regular Sonic and lose a life.
Phase 1: Energy Orbs and Lasers
The Ultimate Gizoid will float around the arena, firing large energy orbs and sweeping laser beams. As Super Sonic, you can fly freely around the screen. Your primary attack is the Super Sonic Boost (B button), which allows you to dash through the Gizoid, dealing damage. Focus on dodging its attacks while continuously boosting into it. The Gizoid will occasionally create a shield, making it invulnerable; wait for the shield to drop before attacking again. Keep an eye on your ring count and collect any rings that appear from destroyed projectiles or from the Gizoid itself.
Phase 2: Increased Aggression and Homing Attacks
After taking significant damage, the Ultimate Gizoid will become more aggressive, firing more projectiles and moving faster. It will also start performing homing dash attacks. Continue to fly around, dodging its attacks, and boosting into it whenever its shield is down. The key is to maintain your ring count by collecting any rings that appear. Tails, as your partner, will occasionally drop rings for you, which is incredibly helpful. This fight is a test of endurance and precise dodging while continuously attacking. Aim for approximately 15-20 hits to defeat the Ultimate Gizoid and complete the game's true ending.