Take a deep breath I reckon, though Its just appalling what that buyer has done. It would have given you such a shock to see, but you can have a red hot go at getting them all removed.

Anyone who looks at the feedback who has half a brain can see that the buyer that has left those negative feedback is a competitor.  And leaving that many negatives at once must raise some red flags at ebays end.

Ring ebay tomorrow, and calmly request for the feedback to be removed as the feedback is malicious and left by a competitor.

Hear out what ebay says. Don't argue with them, it does not go in your favour if you appear argumentative in the slightest. 

If they will not review and remove the feedback, then complete and carefully fill out the feedback removal for defamation forms (search the site map to access) for each and every feedback left - be sure to include the exact reasons why the feedback is untrue and damaging to your reputation as a seller.