What's the top 3 hardest games you've ever played? Here's mine:
#1 Touhou 06-EoSD
boss fight starts at 1:18
[YOUTUBE]lHyW6Gp6UE8&t=1m18s[/YOUTUBE]
On the higher difficulties you literally need to know exactly where to position ahead of time so that you don't put yourself in a spot where a move is undodgeable, it's super fast paced
#2 Tera Online
(mute sound if you don't like the music the guy put in the vid)
In Manaya's Core Hard Mode, practically half of the final bosses attacks one shot you even through the best gear, so you gotta dodge/block them. Eventually later in the fight her animations become so fast that you need to react super quickly, and overall it becomes really difficult.
#3 Vindictus
It's an easier boss, but I felt it captured the idea of what combat is like in that game. This was before they updated the graphics so if it looks ugly don't worry, it looks a lot better now.
At least until the game went pay2win and they made it too easier by removing the potion limit, this game took a ton of skill to play. You needed to time dodges or block attacks really well, and ration your potions/supplies properly and overall just know what you're doing.