What was the hardest boss you ever fought in a video game
I found it was the final boss of Ninja Gaiden
But I also had lots of trouble with the marauder shield in Mass Effect 3 trying to line up the shit before getting killed
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The Fury in MGS3 was ridiculous on higher difficulties. One of the best boss fights in gaming though, having to use stealth and camouflage to get the drop on a massively overpowered foe.