Gladiaron

Gladiaron was a Decepticon general that Sharpedge served under, He was a gladiator in his old days, being a rival of Megatron in the pits of Kaon before joining the Decepticons, and is believed to have once been powerful enough to defeat Megatron 

Though now... he serves as a general himself under Megatron command

History:

Gladiaron was forged during the Nominus Prime era and was a rival to Megatron before he joined the Decepticon cause, for a time he was believed to be powerful enough to defeat Megatron, regardless he became a general under Megatron's command

He was mentioned by Sharpedge during his self monologue about his experience in space[The Confrentation]

Notes:

He's named after G1 Gladiaron