There are some which don’t know who they are like
The other
Stan lee(as he came in evey single movie)

I would go with GROOT. Like we don’t really know where he came from, what are his actual powers, and as such. So in MCU its Groot. And kinda in a way Rocket too. But i like groot more so I would go with GROOT.

Groot is from Planet X a planet thought to have no living species living in it anymore.

The “One-Above-All” is Omnipotent (All Powerful), Omniscient (All Knowing), and Omnipresent (Everywhere). He is the most powerful being in the Marvel Multiverse. He exists beyond space and time. His power is unlimited, incalculable and immeasurable, he cannot be damaged in any way and he has control over all forms of energy. He was first introduced in #Doctor Strange 13 comic
He is the most mysterious character in Marvel no one knows his exact origin

It is groot because we don’t have any information of him