A fitting end would have been his unrepentant death, and after dealing with his insanity after all this time in Season 3, the other Decepticons realize how silly it is to continue the war and give it up.
It does remind me how I wish someone would do something of a more grounded take of the original series and sorting out its scatter brained world building. I'm one that finds the Quintessons and Autobot mythology compatible, with the former effectively being a race of Demiurges that took over and re-purposed Cybertron and the Autobots they built from it for their own ends, and that in the end, the hostility between the two factions comes from Quentessons meddling in their production, if only by making the Decepticons war machines that are compelled by their nature to wage it and find little meaning beyond it.
While they fought and militarily led much of the campaign against the Quentessons, the later Cybertronians Wars came from them finding themselves unable to do anything else, and so turn on the Autobots.
