An Autobot with a limited past, not a lot is known about Onslaught. All that we do know is that he met up with the Autobots (g1) and never left their side since it was unaware if he was before then or not. But he was quickly taken under the wing of one Optimus Prime and followed his ways. He became friends to many Autobots, the ones closest to him being Optimus , Hot Rod (Rodimus) Grimlock , Ironhide ,Blaster , Wreck-Gar and Bumblebee. He learned something from each and every one of them: a great sense of friendship and loyalty to list a few.
He had been with the Autobots aboard the Elpis until the ship got destroyed and was on a mission with friends Prowl, Wolverine and Sari Sumdac until he was bitten by a sharkticon and saved Wolverine from a Sentinel MRK II by being picked up in his place. Needing a new body from the attack he, to help himself and his fellow Autobots, walked into a lake of Angolmois and was reborn into his new unpredictable triple changing mode. Onslaught is REBORN!!! Now learning to deal with Angolmois, he sometimes gives in when he can't. This constantly keeps his mood changing. And his patience is now always Ground ZERO, with just as much tolerance.