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.
Phan Phan qualifies as That One Mid-boss. Between his pattern being randomized, moving insanely fast, and his attacks coming out quickly with little warning, he is by far the most annoying miniboss to fight.
Box Boxer is also very annoying with his constant grabs, throws, and stunlocks.