Death World: In one very real sense, most of them, since most worlds that aren’t your own come complete with an atmohydrosphere that you can’t breathe, a temperature that will probably kill you, and quite possibly a very unhelpful gravity, to boot.  Many of the Apocalypse How worlds also qualify, from things like residual radiation and leftover ecophages.

There’re a decent number of dangerous garden worlds, too, but most of them – leaving aside things like the above, or related syndromes like heavy metal poisoning, biochemistries that interact in a bad way with other people’s, etc. – most of them aren’t all that much worse than, say, randomly selected bits of Earth.  (In-universe, it turns out superhostility isn’t all that viable an evolutionary strategy vis-à-vis the advantages of being sufficiently non-rabid to cooperate.)