Here is possibly the most disruptive build I’ve ever come up with, made entirely with vanilla options form the Core HB and Ultimate line.

Bludgeoner shatter defenses wild shape druid rogue. 9 natural attacks (one bite, 8 tentacles), each attack triggers an intimidation check. Each tentacle triggers a grab grapple check, in turn triggering constrict damage. Each attack after the first triggering sneak attack damage.

Roll just under 30d20, 1d8, 16d4, and x(8d6)* dice a turn, plus however many crit threat/confirms rolls happen. Get an animal companion with the luck domain power for your druid bond, and bump it up to 60d20 a turn. Add a touch damage spell like Pale Flame (CL*2d6) or Chill touch(CLd6) or a Flaming Amulet of Might Fists and the like for even more damage dice.