Scourge

Scourge (Nemesis Prime) is a monstrous Transformer sent to kill Cybertrons (Autobots) and Destrons (Decepticons) alike. It scanned the minds of the Transformers and took the form of Convoy (Optimus Prime), as it was the most powerful and respected in all their minds. As a duplicate of Convoy, Scourge has all of Convoy's strength and power, in addition to its own ability to reconstruct himself.

Nemesis Prime wields the Dark Saber (Vorpal Saber), a twisted clone of the Star Saber, and has a Micron (Mini-Con) partner named Sweep (Run-Over).

(Source: Transformers Wiki, edited)