Sonic 3 & Knuckles: The Challenges: Part 13: Sonic's Final Battle (S-Rank)
45Final Battle has three separate challenges for itself, and each of these challenges focus on different characters facing several of the latest bosses in all of Sonic 3 & Knuckles.
The second Final Battle focuses on Sonic.
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Sonic fights most of the last bosses of the each respective half of Sonic 3 and Sonic & Knuckles.
For the first phase, after being denied to fight it in the 2nd Gravitation challenge, Sonic finally gets to fight Death Egg's Act 1 boss. However, after it's destroyed, the ground does not explode under Sonic's feet. He automatically exits, Stage Right.
For the second phase, Sonic is now immediately in the final boss section of Death Egg Act 2, since Knuckles already beat the regular Act 2 boss before. It is here that Sonic faces the remaining two bosses of Launch Base, including Eggman's Big Arm!
Then, once those Launch Base bosses are dealt with, the third and final phase of Sonic's Final Battle has him take down all 3 segments of the Great Eggman Robo like usual, from the finger fights, to the chest-buster battle, and then end this all with the last Master Emerald chase!
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Afterwards, Sonic's Final Battle is done. That means one more challenge, one more level, and one more character left to use it for...