Meshuggah back in May was the most violent crowd Ive seen, Nevermore on Halloween 2010 was right up there as well.
I got knocked out during Haste The Dayw hen they opened for As I Lay Dying and All That Remains (a couple years before ATR made it big). But thats because I never heard of pit ninjas before nor did I know how to avoid them.
That's about all I got for wildest crowds that actually mattered.
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