P(n) = 1 - (1 - P(1))^n
Abilities: Scrappy, Early Bird, Inner Focus (DW)
Ability: Parental bond (Allows the pokemon to attack twice. The second attack is half as powerful)
Kangaskhan is a Pokemon that every VGC team needs to prepare for. Possessing a fast 90/100 base speed, legendary 105/100/100 defenses post-Mega Evolution, and access to Scrappy pre-mega and Parental Bond post-Mega, there are few Pokemon that can go toe-to-toe with the Parent Pokemon. Unlike some Mega-evolutions like Garchomp or Alakazam, Mega Kangaskhan has no real downside to going Mega. Parental Bond acts like a pseudo-Choice Band without the penalty of being locked into a single move. With access to Power-Up Punch, Crunch, and STAB Return, few Pokemon in the game avoid a 2HKO, and with Parental Bond it will even break Substitutes and Focus Sashes reliably. Unfortunately Parental Bond does not affect spread moves, so moves like Earthquake and Rock Slide do not benefit from its boost, but base 125 Attack is nothing to sneeze at.
Set Name: Kangas-Kangaskhan
Kangaskhan @ Kangaskhanite
Ability: Scrappy/Inner Focus -> Parental Bond
EVs: 4 HP / 252 Atk / 252 Speed
-Fake Out/Power-Up Punch
This is probably Kangaskhan's most common set that i've seen. Pre-Mega, Kangaskhan can run either Scrappy (to guarantee a Fake Out versus ghosts) or Inner Focus, to prevent Fake Out from opposing Fake Out-ers. Post-Mega, the remaining moves will all hit twice (and in the case of Power-Up Punch will also boost attack twice), and from there Kangaskhan can punch holes in the opposing Pokemon. Thanks to Kanga's base 90 speed pre-Mega, the list of Pokemon that can stop a Fake Out is rather small, consisting of faster Fake Out users, the few faster Quick Guard users, and Meowstic.
Bout the only way to stop a Kangaskhan from punching holes in your team is to outplay it, either by resisting all of its attacks, KOing it with faster Pokemon (like Garchomp or Mega Lucario), or inflicting Status such as Burn or Sleep. Sucker Punch can be played around, but many Kangaskhan will carry Crunch instead. It also needs to be wary of attacking Garchomp directly, as many Garchomp have the ability Rough Skin specifically to punish Kangaskhan.