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: Bomber Elite. The majority of the fight he is literally invincible, and new players aren't likely to catch his patterns the first time.
Beauty Bomber of all bosses can be this, since unless you have really good aim with your bombs they're VERY likely to hurt you when they blow up on her shields. To add insult to injury, her actual attacks are child's play to avoid.