One move completely f*cks any Kahn not packing Sucker Punch. And that's King's Shield. Most sets include contact moves and Power-Up Punch obviously can't hit him. Aegislash can come in on a predicted Power-Up and take a hit afterwards with its high defense, then smack him with a boosted Sacred Sword (probably even a +4 if you put it that way, since Weakness Policy is a slightly common combo with him while using Swords Dance).Crunch and Sucker Punch beat Aegislash, no questions asked, should Kang be at +1 from a scrappy PUP.
+1 252 Atk Parental Bond Mega Kangaskhan Sucker Punch vs. 252 HP / 0 Def Aegislash-Shield: 270-318 (83.3 - 98.1%) -- guaranteed 2HKO This is the best possible scenario for slash.
Even assuming it has Sucker Punch it's just mind games at that point for whenever Aegislash will use King's Shield/Swords Dance or when Khan uses Sucker Punch. I still really think Aegislash is a good counter and will OHKO Khan in most instances with the Policy set-up.