Legend of the Guardians: The Owls of Ga'hoole

The only reason this is not trivial is because you'll often run out of enemies before you can get your chain full. I ended up getting this during the second survival challenge. Also, I'm pretty sure you have to get a hit chain of 15 exactly because I could have sworn that I got over a 15 hit chain and the trophy didn't unlock. But when I got a 15 hit chain exactly, it did.