These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Limbo
Alas, Poor Villain: The spider. Despite all the trouble he's been, it's hard to hate him while you tear his last leg off and roll his helpless, limbless body into a pit of spikes so you can progress.
In the ending the boy approaches his sister, who is picking flowers by a rope ladder to some treehouse. The title screen is that same area, only the rope ladder is broken and flies are hovering over what appears to be dead bodies. Theirs?
If Limbo, the outermost edge of Hell, is this threatening and scary... then what's the rest of hell like?
Your deaths, the deaths you inflict, and the er... "objects" surrounding you that you must use to progress. Such as ripping out a one-legged spider's leg and rolling its body into a pit of spikes to cross said pit. Or using surrounding dead bodies as flotation devices, or to trigger traps.
Brain parasites. That is all.
That One Boss: Again, the spider. Specifically, THE one boss, since no others are found in the game.