8. Alexander The IV - Rogue Legacy
Difficulty in games across the last handful of generations used to be far easier. Everything moving on a 2D plane? Just put a ton of things in the way that'll deal damage if the player touches them. Simple. Rogue Legacy, in paying tribute to the glorious 2D days of yore, elected to build one hell of a satisfying roguelike experience where you're meant to journey through the same randomised environments over and over, but peppered each area with some supremely tough boss encounters. https://www.youtube.com/watch?v=YOG3mcrFJ1E Alexander is the worst of the lot; a huge flaming skull that you'll do battle with inside an squared-off arena of spikes. Jump too high and you'll hit them, not enough and he'll get you instead. Oh, and he spews humungous fireballs in four directions every few seconds, so if you haven't got your timing down to exact milliseconds, you're toast. Have fun resetting back the beginning and making the arduous journey to face him again!