Nothing.
There is nothing that can, or will be done about this downvote. If someone triggers the serial voting script, the votes will be reversed, and if you wish to flag a post of yours to have a moderator look into possible voting fraud, that's an option too... but getting a bad post downvoted once is not anything actionable... and now that you've brought attention to it on meta, you can probably expect more downvote(s) on it.
This is the nature of drawing attention to yourself and/or your posts. More eyeballs means more votes. For good contributions, those are upvotes, for bad ones, they're downvotes. This is largely by design and/or human nature, so it's not a situation where anything needs to be, or should be "done about it."
Personally, I'd recommend working on improving your contributions... you have a lot of heavily-downvoted posts that, frankly, deserve downvotes, but other than that, there's nothing to be done.