The Nether is widely regarded as a hell-place. It's filled with lava, treacherous pits, spiders twice the size of a large human, and ghasts. Pigmen aren't much better, but at least they don't attack you first. Wither skeletons roam large areas of ragged half-destroyed fortresses, whose odd corners are guarded by living flames.
It is so easy to get lost in the Nether that some people regard it as a liminal space, not knowing if their portal back will take them to where they entered or someplace completely different.