The Transformers universe.
"Hahahaha! I, Unicron, have returned!"
A steel planet appeared in the cosmos, then began to transform. In the blink of an eye, it became a colossal mechanical god.
"Hehehehe, Primus, are you ready to receive your master's blessing?"
Unicron gazed into the empty space before him. In a battle so long ago that countless years had passed since, he and Primus had fought to the death. In the end, Unicron had fallen into a deep slumber and drifted through space. Vast amounts of cosmic dust had gathered on him, turning him into a planet.
If nothing unexpected had happened, he might have continued sleeping for billions of years, until life called humanity emerged on the planet and a civilization arose. Only when the story truly began would he have had a chance to awaken.
But, by sheer coincidence, something unexpected had happened: he had acquired a chat group. Its stimulation had roused him ahead of time.
However, when he had first awakened, his injuries had not healed. It had taken quite some time for him to fully recover.
Unfortunately, the group members had refused to let him visit their worlds and merge with their worlds' negative aspects as soon as they learned that he was Unicron, a major villainous boss. Otherwise, by his estimate, if he could truly become the negative aspect of other universes, merging once would probably have healed his injuries completely.
If he merged a few more times, perhaps this time Unicron wouldn't be the one to lose.
However, if Unicron really became that powerful, to the point that he could freely travel between universes, those group members would probably be doomed.
Because once he reached that point, Unicron would destroy their universes without hesitation. No, to be precise, he would make order disappear