Generally speaking, it's expected that the first boss in a video game doesn't offer up too much resistance.
Most often, they're intended to serve as a glorified tutorial to the player and basically let them know what they should expect from the subsequent, more challenging "proper" bosses.
But not all bosses are created equal, or rather, not all developers are interested in just throwing you a nerfed chump boss right out of the gate. In most games dying at the hand of the first boss is something to be embarrassed about, but in these games it was a damn-near eventuality.
These games all pitted players against first bosses who weren't just going to hand you a win - they all put up one hell of a fight and, if you went in complacent or unprepared, they absolutely made short work of you.
Some players may have even spent literally hours on these bosses, such is the baffling level of difficulty they presented. But when you finally triumphed over them - assuming you did - you were left fully battle-hardened for the true challenge that lie ahead...
10. Kuze - Yakuza 0
As a prequel to the mainline Yakuza franchise, Yakuza 0 served as an entry point for many new fans, and is largely credited with boosting the series' popularity over the last few years.
Though the game eases players in gently with reams of cinematics and fuss-free combat, the first boss battle against Tojo clan lieutenant Daisaku Kuze represents a massively challenging skill-check.
Those new to the series were blindsided en masse by the ferocity of Yakuza 0's first boss, who due to the player's relative weakness and lack of combat abilities at this point ends up being one of the game's very toughest bosses.
He's got a massive life bar, can counter most of what you throw at him, and if he locks you into a combo attack you can lose massive amounts of health.
To make matters worse, you have to battle your way through a fleet of goons before making your way to Kuze, and because the game's checkpointing is just God-awful, you're forced to go through it all again if Kuze defeats you.
It adds up to a frustrating difficulty spike that caught many players off-guard, if also ensuring they knew what to expect moving forward.