Mr. Einhorn, 47, whose fund at its peak owned 6.8 percent of the company’s shares, remained bullish on SunEdison’s prospects even as the stock, which was trading at about $31 a share last summer plunged during the remainder of the year. In early January, as SunEdison shares were trading at $3, Mr. Einhorn got a representative appointed to the company’s board.

Then on April 21, the company filed for bankruptcy. Shares now trade for around 24 cents.

Calculating specific losses for a hedge fund is difficult without knowing the prices which a firm purchased its shares. But Valeant’s and SunEdison’s plunging share prices have caused considerable carnage.

It is a time of turbulence for the hedge fund industry, where some of the biggest names have reported double-digit losses. Last year, firms fell deeply into the red after wide swings in certain so-called hedge fund hotel stocks, leading what Daniel S. Loeb of Third Point Management called a “hedge fund killing field” in a recent investor letter.

The total value of hedge fund positions in SunEdison, which once accounted for 66 percent of the company’s shares, is now worth just $15 million after its bankruptcy filing, according to FactSet, the financial research firm. Before hedge funds began selling their SunEdison shares last year, the value of all of those firms’ holdings was $3.5 billion.

The losses are worse with Valeant. At the beginning of 2015, hedge funds owned about 23 percent of the company’s shares. Today, the market value of the industry’s holdings in Valeant have fallen by $7.3 billion even as hedge funds bought more, according to FactSet.

Firms have until mid-May to disclose whether they sold or bought shares in the fourth quarter.

That so many hedge funds remained bullish on Valeant despite months of turmoil — as questions were raised repeatedly about its accounting practices — reflects the difficulty managers sometimes have with changing course.

“We all get lazy and when an idea seems to be working — inertia tends to take over and you stop paying attention,” said James Chanos, the founder of Kynikos Associates and one of Wall Street’s best-known bearish investors. “That’s on full evidence with Valeant and SunEdison too,” he added.