So I ran a calculation, and apparently, max Defense Sableye is only 3HKOed by Mega Kangaskhan's Crunch:
252+ Atk Parental Bond Mega Kangaskhan Crunch vs. 252 HP / 252+ Def Sableye: 121-144 (39.8 - 47.3%) -- guaranteed 3HKO
Now I know that maximum Defense Sableye is significantly rare, but if such a scenario occurred, would Crunch be Mega Kangaskhan's best option against Sableye, and wouldn't Sableye be able to retaliate with Will-O-Wisp, or can Mega Kangaskhan still get past Sableye through conventional means? I apologize if there's something I'm missing here, this just had me wondering.
Earthquake 2HKOes if I recall, which is an issue. Also, if Kangaskhan doesn't Megavolve on the switch and scores a +1 things become significantly more dire. (For that matter, if it's already +2 you're kinda screwed)
EDIT:
Jaded_Hades -- The Foul Play point is totally irrelevant because a +2 Kang will OHKO Mabdibuzz with Return...
+2 252+ Atk Parental Bond Kangaskhan Return vs. 252 HP / 252+ Def Mandibuzz: 195-231 (89.8 - 106.4%) -- 37.5% chance to OHKO pretty much confirms this. I mean, Kee/Chilan will allow Mandibuzz to soak the attack but at the cost of significantly worsening it in other situations.