Ummmm if by creation you're mistakenly meaning a universe then yes you have that feat right for Unicron. NJ are you trying to fool those people who might not have the thread? Naughty, naughty. Unicron as his biggest feat has eaten a universe. His hunger satiated he fell asleep.
good battle, hmmm I would say Galactus would be the first to fall since he is just a part of the Marvel Multiverse and has never been shown to live outside it. Imperiex and Unicron have destroyed both of there universes before and have lived in the Void, I would say Imperiex Prime could win since he is the embodiment of entropy (the void).
Now he isn't even the embodiment of Destruction anymore wow you are trying to destroy Unicron now aren't you. Well I tell you what Galactic let everyone read the Phoenix vs Unicron thread and let them decide.
I don't think it's an assumption GS, Unicron was a primal chaotic energy that embodies destruction. This is before the big bang that created the current universe, the only difference now is that this eergy now inhabits a physical form.
time is nothing to Imperiex either, he was a threat that not only threated 1 timeline but every time in Hypertime DC, having his armor open would have destroyed everything in creation. Imperiex was planning on having massive black holes to destroy everything then it would remake a new big bang, if he wanted that to happen he can live through it as well. Imperiex Prime wins.