Death Egg Zone
From Sonic Retro
Death Egg Zone is the 11th and final zone in Sonic 2.
It consists only of 2 short walkways leading up to 2 boss battles: one against Mecha Sonic (8 hits) and one against Dr. Robotnik's giant robot replica of himself (12 hits).
After defeating the second boss, Sonic runs off the edge of the exploding Death Egg, ending the level and leading to the Sonic 2 ending animation.