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.
That One Boss: Samson since he can kill you in 5 seconds because of the disjointed hitboxes and he jumps. Unless you're really good at jumping... and have good luck...
Thor's first and second forms can become this. More his Phoenix form that his other.
That One Level: Dwarf Cave's first main section has a ton of pitfalls. Which is instant death.
Particularly any long level is a much weaker version of this trope, since everything looks the same. Hope you got a map!