One stock has been a surprise winner on the S&P 500 this year: Coty.

The beauty retailer has exploded 102% in 2019, by far the best performer of the benchmark index.

However, it is also the most shorted stock of the S&P 500 at 50% of its float.

High short interest could squeeze out more gains in this rally over the short term, says one technical analyst.

"Near term the stock is still quite bullish," Mark Newton, founder of Newton Advisors, said Wednesday on CNBC's "Trading Nation. " "Technically the stock has started to act quite well, breaking out on very heavy volume, almost three or four times average of late. I see the stock going to $14.50 to $15 near term."

Anything past that critical level looks like a tougher ask, though, says Newton.

"You do see some headwinds right near $15. The stock did come down from a high of over $30 back in 2015," said Newton. It's "still coming down off a big, long decline in the stock … For investors, it needs to clear $15 to really be out of the woods."

Mark Tepper, president of Strategic Wealth Partners, says fundamentals also don't support a long-term breakout.

"Their overall strategy, in my opinion, is still flawed," Tepper said during the same segment. "With their acquisition from P&G, they've basically doubled down on mass consumer, but consumer buying trends have changed. Consumers now want experience, they want prestige, they want boutique, not CoverGirl. And [Coty's] debt levels are sky high."

Tepper instead prefers another beauty stock over Coty.

"If you're going to be in this space I'd rather own Ulta. It's a better company, no debt, and it gives you exposure to whichever brands are in favor at that given time, " said Tepper.

Ulta Beauty has also had an impressive year, rallying 41% since January. That puts it on track for its best year since 2015 when it went public.