Quote Originally Posted by Zahhak View Post
Other then animated Black Aracnia I don't know of any other Autobot gone Decepticon story arc or character.
Armada Wheeljack? Cybertron Mudflap? Shattered Glass Sideswipe? Universe Obsidian? Classics Cliffjumper?

There were many Maximal to Predacon or Vehicon changes in Beast Wars/Beast Machines as well - Rhinox... Silverbolt... arguably any of the Maximal protoforms that became Predacons...