Mega Kanghaskhan looks decent, but I think that the Ability will change from whatever ability she had (Scrappy, etc.) to Parental Bond.
Now that we know its effect (grants all attacking moves double attacking status), and assuming it doesn't negate the move effects, let's look at some moves that Parental Bond breaks...
Circle Throw: Oh god, can you imagine this? Being able to not only shuffle your opponent's team, but it can possibly reveal half the Pokemon on your opponent's team? And deal entry hazard damage to two Pokemon? Wow...Just wow...
Double-Edge/Giga Impact: I don't even have to explain exactly how broken these would be. 120/150 BP + STAB? You can basically OHKO almost any non-Ghost Pokemon at the cost of 1/3 to 1/2 of your own health or your next turn.
Outrage: Not as powerful as STAB Double-Edge, but it takes care of Dragons should you see one.
Stomp: Assuming the effects of Megaskhan's moves stay in effect, would the 30% chance to flinch be the same or effectively doubled?