Nothing can be done. As I pointed out in my latest post Cooperation is Humanity's greatest asset while abuse, its opposite inevitably leads to mutual destruction.

Steem I think has ways to avoid abuse but we'll have to see how it all plays out.

I think if he removed his down vote before the post payout you would get back your reputation.

I flag many of his post which were simply repost of other articles without any proper attribution.

He needs to realize the sooner he'll act benevolently we'll all be better off including him.