The lack of Star Power wasn't doing him any favors, either.
Most people who play Dark Souls with a regular controller give up after several hundred deaths, and this guy beat it with a character who was barely listening to him. Playing Dark Souls with a Guitar Hero guitar is like teaching an actual person to fight skeletons using only an electric guitar for communication and holy shit we just came up with the sweetest idea for a kung fu movie ever.
Oh, and this guitar killer isn't the only gamer to think of doing something impossible with something stupid. A Destiny player recently went into a six-man raid by himself and defeated Crota. And before you shriek "Crota's only like level 32! Anyone could do that!" keep in mind that this Crota-slayer was using a Rock Band drum kit.
Still easier than playing "YYZ."
Another player with more determination than hobbies managed to beat Soul Calibur on the hardest difficulty with only a Dreamcast fishing pole. And that thing didn't even really have buttons. He had to execute precision martial arts by waggling a plastic fishing pole at his TV and cranking on the reel, which is probably only slightly easier than catching a real fish with karate.
Which is in fact what inspired the Wii Remote.