Technically, although nobody will use Aerial Ace on Serperior, and nobody will fight Emboar with a Serperior. Except ... an idiot? The guy on the picture above.
252+ Atk Choice Band Serperior Aerial Ace vs. 0 HP / 0- Def Emboar: 292-344 (88.4 - 104.2%) -- 31.3% chance to OHKO
Here is the calc of a Serperior using Aerial Ace against an Emboar under every weakening circumstances for Emboar's HP and Defense, and every strengthening circumstance for Serperior. But still, chances to OHKO are pretty thin.