The defeat 800 enemies in 10:00 minutes challenge level on Hyrule Warriors is freaking IMPOSSIBLE!!! As soon as you start making good progress, the game bum-rushes you with 2 King Didongos, the fire-powered guy Volga, a Wizrobe, and a bunch of henchmen including the mummy things that freeze you in place. And Volga takes so much damage from you so freaking fast! So you can't just ignore him and focus on lackies.
And then, if you're lucky enough to defeat all those bosses, the game punishes you for taking too much time on the bosses! There's no pleasing this level!