Who is the greatest villian in terms of being just pure evil. We all know that Eggman is the de-facto villain in the Sonic series but who do you think is the most evil out of all of them.
Dr. Eggman: You know, you love him *or hate him*, the fat man behind nearly every freaking scheme in each and every game.
Eggman Nega: Descendant of Eggman and is even more cruel and calculating than Eggman himself.
Metal Sonic: The most dangerous robot Eggman has ever created. Despite being a robotic copy of Sonic he has a aggressive and very cold hearted personalty, even to his so called creator. He's probably the most powerful thing Eggman created since Sonic Heroes Metal Sonic has copied nearly every character's abilities including Chaos.
Chaos: The immortal near godlike liquid creature that resides in the Master Emerald. Chaos once brought the world to ruin by the acts of the Echidna tribe, first becoming Perfect chaos and flooding it with water. Chaos was originally a chao transformed by being in contact with the Master Emerald.
Black Doom: Leader of the Black Arms and their race. His blood was used to create Shadow which makes him the biological father of Shadow and how he has many other abilities. He planned to devour the Earth but was stopped by the combined efforts of his own creation and Professor Gerald's most devastating weapon. The Eclipse Cannon.
Mephiles: The dark personalty from the Solaris project which he and Iblis we're one and the same. Unlike most villians, he is cold and shows no compassion what so ever as his goal is to re-merge with Iblis where most others are driven by a lust for power. He himself fooled over eleven people from differant time zones to get a perfect result in the present.
Erazor: A malevolent genie, a twisted version of the genie from Aladdin. He planned to warp the story of Arabian Nights and head into Sonic's world. He is defeated when his own lamp is used againest him.
Pir'Oth Ix: The lead villain in the Dark Brotherhood. Lead the Nocturnus Clan againest the ancient Echidnas until the incident with Perfect Chaos. They we're warped to the Twilight Cage mysteriously and forced to change into a sinister technological race. They try using the Master Emerald to transport back but is Twarted by Sonic's gang and a traitor: Shade.
Black Knight: King Arthur, a once noble and legendary king corrupted from becoming immortal. When defeated his powers are taken by Merlina. Although the true foe was Merlina in the end, her actions we're to protect the ancient world while Arthur's was to conquer it and later destroy it.
Dark Gaia: An enormus monster who represents night and destruction. Eggman hoped to use it to conquer the world but it's energy proved far to destructive and started to ruin the world he was going to conquer. Dark Gaia was stopped by it's opposite Light Gaia with aid from Super Sonic.
Take your pick