With shares up over 730%, Tesla bears have seen more than $38 billion in mark-to-market losses this year, according to data from S3 Partners. By comparison, the next-biggest loss for short sellers was on Apple Inc., at just under $7 billion, S3 data shows.

This "is not only the largest mark-to-market loss for any stock this year, it is the largest yearly mark-to-market loss I have ever seen," said Ihor Dusaniwsky, a managing director at S3 Partners.

Tesla didn't respond to a request for comment.

For now, the electric carmaker and its investors, small and large, have the upper hand against a group of short sellers that have come to be known as TSLAQ -- Q being the character exchanges tack onto a stock ticker after a company files for bankruptcy.

Those short sellers include some high-profile names such as Jim Chanos, president and founder of hedge fund Kynikos Associates. Chanos recently reduced the size of his trade, telling Bloomberg TV early in December it's been "painful."