The MCU is a terrifyingly expansive fictional space at this point. It's easier to think of comics characters they HAVEN'T added. But some are just too darn powerful. Like, there's no way to conceivably put half these guys in a movie and have it be to any degree balanced. The Marvel cosmic space is so densely populated with godlike deities and space monsters that you can't swing a dead space-cat without hitting something more powerful than you can comprehend. So here, for your pleasure and enjoyment, is a list of cosmic and magical and other assorted Marvel characters way too powerful for Avengers 4.
10. The Rest of the Elders of the Universe
Well here would be some catch up the film series could do, but probably won't.
The Elders of the Universe are a group of cosmic deities that have always existed. They are most notable for being the temporary caretakers of the Infinity Gems before Thanos got his hands on them. And we've actually already met two in the MCU!! The Collector, who debuted in the post-credits scene of Thor: The Dark World before having a featured roll in Guardians of the Galaxy and probably dying in Infinity War. He also appears in the Guardians ride at California Adventure.
The other MCU Elder is the Grandmaster, who appears and is probably murdered in Thor: Ragnarok.
But there are more unexplored Elders! Among them are the Champion, who likes boxing people all the time because he's super aggro and is totes into punching. Also the Runner, who races faster than any other being in the cosmos. And finally, the Gardener who"¦ sucks. I guess that's his thing.