If it's ability is non-dreamworld then there's nothing special about this Larvitar, considering you can teach Larvitar Superpower in HeartGold.
Now if it's ability IS dreamworld then we have something special on our hands, as Unnerve Tyranitar cannot learn Superpower by any other means.
And yeah, Chople Berry is easy to get now. But isn't it available in the Dream World?
Black FC: 2537-3042-2350
VGC2012 Analysis: Slowbro