Let's say i have a Skuntank with Explosion or any other Self-Destructive move (Is that even possible?). I use Explosion. Does Aftermath activate or....?
If this Pokemon is KOed by a contact attack, the attacker takes damage equal to 25% of its max HP-Smogon
So no slef destruct or explosion will not activate seen as it is self harm, though if the opponent used Close Combat on you and killed skuntank, the opponent would loose 25% of maximum hp.