Knowledge Reigns Supreme Over Nearly Everyone
KRS-One is considered to be one of the greats, both solo and with Boogie Down Productions. Everyone knows Sound of da Police and few come close on vocabulary and relevance. He's also responsible for the worst live performance I've sever seen.
I can't remember exactly when it was, but it was around 2004 and at the Hammersmith Apollo. He was an hour late, and bought around 15 hype-men on stage with him who would shout over each other while trying to get the crowd to make enough noise to bring KRS on. Eventually he gets on stage, does something alledgedly freestyle (though the claim of it being freestyle took longer than the actual freestyle) before leaving the stage again.
And that was pretty much how it went for around half an hour before the venue's curfew bought the show to an end. He didn't perform anything that well known, and everything bathed in the noise of more than a dozen others shouting the rhyming syllables on each line.
The only other show to come as close to these levels of shambolic was Madlib. HE also didn't perform anything very well known, and instead played some deep cuts in a way that just made it obvious he didn't want to be there, while getting hostile with a crowd who unsurprisingly weren't feeling.