Lol, it really depends on the fic, what kind of post-apocalypse it is. I wrote a post-apocalyptic Boxcar Children fic for Yuletide but it was really just a modern reinterpretation of the whole story with "the kids are on their own because virtually all the adults died of a plague" (and it was what the recip had requested - when I saw that prompt, I had to write it, even though it took ages because it ended up 17k, lol).

For Alphas I combined canon divergence with AU - because the final episode of the show (total cliffhanger, btw) had them trying to stop "the end of the world" (had to do with killing off much of the population of the US, I won't spoil the show by saying how). And if one or two things had happened otherwise, it *would* have happened, too, so it was easy to just diverge along that path and end up with them trying to survive. I only got about seven short stories into the series, though (only about a week after the apocalypse), so I hadn't gotten to them seeing other survivors yet.

I honestly have no idea what you mean by "Into the Badlands" - never heard of that.