MCU: 10 Insanely-Powerful Villains Who Could Be The New Thanos
8. The Sentinels
Keeping on the X-Men for a bit longer, you can't have an X-Men story without their primary predators - the mighty Sentinels - making an appearance at some point.
Now, the backstory behind these robots is quite a bit more complicated than it really needed to be, so hopefully the MCU will heed the lesson of Days Of Future Past and just let them just be what makes them such a threatening presence: giant robots programmed for genocide. Not sure why the various writers working on and off X-Men felt that that wasn't enough for us to take them seriously as a threat, but whatever.
The point is, everyone loves giant robots, and given the right production team (which Marvel will inevitably have) these guys could become even more iconic a foe than they already are.
The X-Men have a lot of larger than life foes, so if the first one you show off is "an army of giant robots that could crush Ultron like a tin can" and they're just the first big threat, it'd be a great way for Marvel to demonstrate that they aren't screwing around.