The hideous giant brain guy is one of many beings, native and otherwise, who enjoyed the brief rebirth of gladiatorial combat on Cybertron under the aegis of the alien criminal Zabra. He is mainly noteworthy because, seriously, what the hell.
Marvel Comics UK continuity
The hideous giant brain guy attended the "games" at the Jekka Ampitheatre in Tyrest on the day of Ultra Magnus' bout against the alien Hooligan. He was last seen asking a souvenir salesman about the price of a foot belonging to a defeated combatant. Presumably, when Magnus defeated Zabra and shut down the games, he found something else to do.
He appears to be wearing a Decepticon tattoo on his frontal lobes. Now that's a fanboy.