10 Transformers Who SWITCHED SIDES
2. Optimus Prime (Prime)
Surprised? As was I when I witnessed the great Optimus Prime, paragon for justice and freedom, leader of the righteous Autobots, take Megatron's hand and join him upon the Nemesis at the end of Transformers: Prime's first season.
Okay, okay... so, maybe it wasn't exactly Optimus Prime per say.
After defeating Unicron with the Matrix of Leadership and thus dispelling the power of the primes, Optimus reverted back to Orion Pax, his pre-prime librarian self.
With no memory of the Autobot/Decepticon war, he trusted the only face he knew: Megatron's. He was welcomed aboard the Decepticon warship, fitted with a Decepticon insignia and set to work decoding records from Iacon - information that would prove instrumental for the following episodes.
Thankfully, his time as a Decepticon did not last long. Due to the relentless efforts of the Autobots (who literally went to the moon and back for him) Orion Pax was restored to Prime. Hallelujah!