Doctor Eggman

Doctor Eggman is the main antagonist of Sega's Sonic the Hedgehog series and his original designer was Naoto Ohshima, who created him as one of the many designs for the company's new mascot. He was eventually made into the archenemy of the series' titular main character. Dr. Eggman is a rotound mad scientist who plans to conquer the world in order to build his own Eggman Empire.

Early Life
In his childhood, Ivo Robotnik looked up to his grandfather, Professor Gerald Robotnik, as a hero and believed him to be a great man who had done his best to help mankind. Thus he decided to follow in his grandfather's footstep and became a scientist, as well as pursue a teaching degree. However, he became obsessed with the idea of the entire world under his rule, utterly convinced with his twisted belief that the results of a world conquest orchestrated by him would make the world a better place and benefit all of it's inhabitants. Using his unmatched genius, Doctor Eggman began his plans, spending his entire life on his self-righteous mission.

At some point after setting out on his quest for global domination, Eggman met Sonic the Hedgehog. While the nature of their meeting is unknown, the two of them eventually became rivals, with Sonic proving to be Eggman's greatest enemy. After their meeting, Eggman made several attempts to conquer the world, but at every turn, his plans were laid to waste by Sonic.

Sonic the Hedgehog (1991)
Robotnik's first appearance was in the 1991 video game Sonic the Hedgehog for the Sega Mega Drive/Genesis. He attempted to find the powerful Chaos Emeralds by conquering South Island and turning it's animals into robots. Launching a full-scale assault, Robotni was able to seize control over countless cities, factories and lands, and transformed them into his image and polluted the very environment with his fortresses. Robotnik ordered his vast army to search for the Chaos Emeralds and build weapons of mass destruction so that his dominance would never be challenged. Luckily, Sonic the Hedgehog sped to the rescue, defeated the doctor, saved the animals from being turned into Badniks and retrieved the Chaos Emeralds. Thus the island was restored to it's former peaceful state.

Sonic the Hedgehog 2 (8-Bit)
Robotnik kidnaps Tails for ransom in an attempt to lure the Chaos Emeralds from Sonic, stating that the only way he can get Tails back is to give him the emeralds. Sonic seeks out to get the Chaos Emeralds, beat Robotnik and rescue Tails. Robotnik is eventually defeated when Sonic defeats his last mecha at Crystal Egg Zone, and then saves Tails.

Sonic the Hedgehog 2
The notorious Robotnik created the Death Egg, a huge, orbital space station during another attempt at world domination. He attacked West Side Island, turning it's animals into robots and searching for all seven Chaos Emeralds. He was intercepted by Sonic and his sidekick, Miles "Tails" Prower, who saved the animals and retrieved the Chaos Emeralds before the mad scientist. Sonic infiltrated the Death Egg, sending the space station crashing back to Earth and defeating Robotnik once more.