Everything about those lines and shadowy appearance screams villain, so it can't be Aokiji.
The person is clearly using a technique on law, which also doesn't fit with Aokiji.
It does fit with Doflamingo, with his ability to control people.
I doubt it's Vegapunk either. Despite his frequent mentions, I think he's actually too foreshadowed to be just appear himself.
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http://i498.photobucket.com/albums/rr345/Rakaputra/pjbasis.png
SuperNiceDog - 1, pjbasis - 0