Posted by Talon

They both protect against Fake Out, but here's something interesting:

Lead with Sableye. It is the textbook perfect counter to Mega Kangaskhan. Priority Will-O-Wisp renders it useless for the rest of the match, and is unaffected by Return and Power-Up Punch. Even Kang's most reliable Dark attack, Sucker Punch, can't hit Sableye since Sableye does no damaging moves other than the fourth. Even if it hits, it's bad damage due to the burn and neutral non-STAB.

And he's not affected by Fake Out either.

Sableye @ Leftovers
Ability: Prankster
EVs: 252 HP / 252 SpD / 4 Def
Calm Nature
- Will-O-Wisp
- Taunt
- Recover
- Foul Play / Knock Off / Night Shade

Foul Play destroys anyone setting up on Sableye, or any powerful physical attackers in general. Knock Off can absolutely cripple some Pokemon who are reliant on their items like Talonflame or Dragonite. Night Shade is reliable, and always hits for 100 damage. I'd suggest the first two, or even Toxic if you want to piss him off.

If your priority Will-O-Wisp hits him, this is Kang's only way of hitting Sableye:

252+ Atk Parental Bond burned Mega Kangaskhan Earthquake vs. 252 HP / 4 Def Sableye: 109-130 (35.8 - 42.7%) -- 94.5% chance to 3HKO after Leftovers recovery

Which you can outstall easily with priority Recover.