Death Egg Robot

The Death Egg Robot (aka the Giant Mech) is the final boss of Sonic the Hedgehog 2. It appears as the second boss of the Death Egg Zone in that game, and is fought immediately after Silver Sonic. It looks much like a giant robotic Dr. Eggman, but is in fact a suit piloted by the real Robotnik. It is very difficult to defeat as there are no rings in the entire stage.

Boss battle
After beating Silver Sonic, the real hedgehog chases after Robotnik, who escapes into the Giant Mech. It just moves very slowly and the player has to jump and hit the body to damage it, which is harder than it sounds because if timed wrong, the player may touch one of the hands and die. After a while, the Mech will fly up and a lock-on target will appear and follow the player. Soon, the lock-on will start flashing and the Giant Mech will slam down. When it comes down, its hands will fire, attempting to hit the player. Repeating the process, the mech will break down and explosions will follow the player as Sonic (or Tails) will throw themselves out of the Death Egg into space.

Ending
If the player gets all the Chaos Emeralds and finishes as Sonic, a storybook-like ending will play with Tails and the small animals watching the Death Egg explode. Tails then gets into the Tornado so he can start adventuring, while flying, he spots Sonic, who activated his Super Form, Super Sonic sometime after escaping the Death Egg. The two then fly away and fly toward the screen. If the player fails to get the Emeralds, the ending is the same, but Sonic will land on the wings of the Tornado and will jump toward the screen.

Sonic 4
The Giant Mech also appears in Sonic 4, where it is the same as the Death Egg robot from Sonic 2, but like the other bosses in Sonic, it has new moves after being hit multiple times. After sixteen hits, it becomes surrounded by electricity, making it impossible to damage. It can also leap across the field both forward and backward and fires its rocket hands much faster. To damage it, Sonic must knock its rocket hands back into it when one flies off and floats back down. This disables its electrical field long enough to get some hits in. But after about 6 hits Death Egg Robot starts to shoot lasers at Sonic. There are 2 types of lasers, the first being the pink lasers commonly used by many other enemies and second a beam similar to the Sonic Advance lasers.

On its last hit, the Mech will fly up and attempt to destroy the ground to drop Sonic into a pit. It must be hit before the floor falls apart to clear the game. If the player doesn't hit the robot in time the Mech will break the floor causing you to fall and lose a life. This move is similiar to the Egg Viper's last attempt to defeat Sonic.

Sonic Generations
For more, see: Death Egg (Sonic Generations)

In the upcoming game, Sonic Generations, the Giant Mech is a boss fight in Death Egg, after Sky Sanctuary, representing Sonic the Hedgehog 2.

Adventures of Sonic the Hedgehog
The Giant Mech appears in the episode "Momma Robotnik's Birthday. It appears where Momma Robotnik shows a video to Tails about Robotnik where you see he is on it then he fell down when the robot moves, although the Giant Mech is actually a robot instead of Eggman in it.

Sonic OVA
Robotnik has a machine called Metal Robotnik which is largely based on the Giant Mech.

Sonic the Comic
The Giant Mech (referred to only as Robotnik's "deadly battle armour") appeared in flashback in Sonic the Comic #27, "Part 2: A Tale of Tails". The main events of Sonic the Comic take place after Sonic 2, and in the story in question, the Giant Mech is revealed to have played precisely the same role as in the game: Sonic fought Robotnik aboard the Death Egg (with Robotnik in the Death Egg robot) in order to prevent the satellite's operation.

Archie Comics
Although the Giant Mech itself did appear, Doctor Robotnik did wear a powered suit of body armour called the Eggs-O-Skeleton in Sonic Quest #3, "Over Easy", as part of Archie's adaptation of the Death Egg saga. The real robot appeared in Issue 229.