The Marvel Cinematic Universe is terrifying if you really think about it.
There are dozens of beings just on this planet that could destroy the earth with their own power.
Then you have the Celestials, Thanos (who plans to murder all of reality, or half, depending on his mood), Shuma Gorath, Mephisto, Surtur, The Kree Empire, the Chatari, the Skrulls, Dormammu, Nightmare, Loki with the OdinForce, Graviton, domestic terrorist organizations like AIM/Hydra/whatever the fuck they're doing on Agents of Shield, foreign terrorist organizations like the Ten Rings, secretive nation superpowers like Wakanda, Atlantis, and the home of the Inhumans, and the countless psychotic street-level villains who wouldn't think twice about offing a few civilians.
That's not even counting all the horrifying shit we'd be facing down if the Fantastic Four, mutants, or the Shi'ar were allowed in. Franklin Richards, the Annihilation Wave, Galactus and the Ultimate Nullifier, Doom, Apocalypse, Sentinels, Onslaught, The Juggernaut, The Phoenix Force, and Gladiator. Yeah no. Come to think of it, Fox could do some awesome cosmic-level shit if they really wanted to, but that's none of my business though.