Megidramon

Megidramon is an evil Mega form of Guilmon.

Appearance
He has wings, claws, and a snakelike tail in place of leg, and drools acidic slime.

Role
Guilmon digivolved to Megidramon when Takato, enraged over Beelzemon killing Leomon, ordered him to digivolve to Mega. Megidramon had a hazard sign on his chest that threatened to destroy the digital world. Megidramon pinned Beelzemon to the ground, intending to eat him.

However, when Makuramon appeared, Beelzemon destroyed him and absorbed his data, and did the same to Terriermon and Renamon's Ultimate forms (though they survived), enabling him to overpower Megidramon. Takato was then able to get through to him and turn him back into Guilmon.

Trivia

 * Megidramon is similar to SkullGreymon from the first season. Both are a corrupted form the main Digimon turns into due to their partner going about digivolving them the wrong way.