Editing Post-Apocalyptic (section)

====The Big Ones====
No escape. No respite. Not even immortal beings can survive these. Worst of all, a few are inevitable, and the universe will never be the same. The existential dread is natural, but luckily most of these final doomsdays are so far off or so unlikely that humanity will likely have lived out its existence long beforehand. If not, we'd probably be so far along that we could just jump ship into another universe, either a natural one in a multiverse or an artificially created one. But adding 'post-' to these apocalypses is not really possible.
*Stellar decay - by the appropriately named "degenerate era", stars capable of supporting life will have burned out due to a lack of fuel, and no more will be made (if the universe is infinite, there may be infinite material for star formation but there's also an infinite amount of stars to use it up). Life developing as it did on Earth will be impossible, and unless humanity or some other advanced species has the means to keep the torch lit, life will cease to exist.
*Proton decay - unproven, but if it exists, there's a lifespan to solid matter that isn't part of a black hole. This would be a hard limit on life's possible existence with or without human intervention. If not, humanity may survive by leeching energy off black holes until the universe itself ends.
*Death of the universe - whether it crumples back into a point, rips itself apart, or becomes an empty, cold wasteland of nothingness, the universe WILL die, and there's nothing you can do about it. On obscene timescales even black holes disappear, which is the hardest of hard limits on existence. Past this point, time becomes meaningless, unless by some miracle an anomaly causes another Big Bang.
*Vacuum decay - helpfully described as "the universe's delete button" by a certain German duck, this is essentially what could happen if some of the universe suddenly received an update to its physics engine. Long story short, a sphere of nothingness expands at the speed of light, destroying everything and leaving behind a portion of spacetime where our laws of physics no longer apply. Given enough time, probability will spawn enough of these to clean up whatever remains of the universe after its death.
*The Off Switch - an ever-present threat if the simulation argument is true is that whoever made the simulation could get bored and just turn the 'game' off forever, or some accident happens in the real world that shuts it down. Temporarily turning it off isn't really a threat, for in all likelihood it would just resume where it left off, and we would be none the wiser. A meta version of post-apocalyptic fiction could be following the creators of a simulation after turning it off permanently, and how said simulation affected their society.