In video games, the concept of an end of area or level boss is something of a common trope (I mean look at the number of videos we alone have done on the concept), and as such, I think we're all starting to understand what a "boss" is no matter how it's dressed up to the player.
Whether it's covered in spikes, slime has enough individual appendages that animating it must have been an utter nightmare or is just straight up mean enough to beat up your dad, a video game boss is basically a test of your skills up until that point in time, and can be used to teach the player a new skill or make them use a new ability in direct battle in order to master it for future conflicts.
However, that doesn't mean that all bosses abide by a gentle difficulty curve as in some cases opening or early game bosses can utterly kick your ass! This is like throwing someone in at the deep end but then pointing out that the water has been replaced with acid.
Prepare to get your skin melted and your bones broken, because these bosses weren't messing around.
8. E.M.M.I - Metroid Dread
When Metroid Dread began its marketing run and seemed to be pushing an unsettling horror front and center, fans around the world sat up and took notice. As a character, Samus is often shown to be on the back foot, but here, the game was suggesting that there would be some fights that would be so utterly one-sided that even this galactic bounty hunter would be left quaking in her boots.
And upon finally confronting the robotic murder machines known as E.M.M.I's, yeah you can kind of see why. As they are utterly brutal!
The first meeting I had with one of these beasts was extremely short, as while other enemies will give you a pretty lengthy window of opportunity to hit a counter, the devs decreased that window immensely. Now Samus would have one, split-second opportunity to escape or that was it, one hit kill, you're done.
I doubt there was a single-player going that managed to escape first time from these hunter-killers, especially in the early stages when you're just getting your bearings. Being chased through a section you're only seeing for the first time in that desperate flight increases the chances of mistakes, and one is all you'll need to get that special E.M.M.I soul-sucking kiss.