No Alternate Origins: All powers came from The Event. No gamma rays, cosmic rays, radioactive spiders, or super-soldier serum.
No Parallel Universes or Time Travel: While M Theory states that parallel universes probably exist, there is no way to travel between them. And Time Travel is definitely possible, in the form a travelling to the future at a rate of one second per second.
Death is Death: No resurrections, no Lazarus Pits.
No Cosmic: To quote the great Douglas Adams, “Space is big. Really big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.” Aliens, alien worlds, other earthlike planets are a no no. If you were immortal, and could survive in space, and travel in space, and didn’t need things like food or water, you might be able to find aliens. It’d take a really really really long time to do so though.
No Supernatural: This is not Buffy or Dresden Files. Things like heaven, hell, demons, angels, gods, devils, magic, and magical creatures are strictly in the realm of philosophical debate and/or fiction.