Mega Kangaskhan has an untauntable massive attack boost in power-up-punch and can subsequently smash most common walls. Further more, it can out-speed most walls, has good survivability with its 105/100/100 defenses, can sucker-punch most revenge killers, doesn't give a damn about substitute or sturdy or focus sash, and has absurdly specific gimmick counters like that rocky helmet.

Did that once
Got swept by special attack mega Kangaskan. . .