One stock helped decimate Bill Ackman's hedge fund performance (VRX)

Bill Ackman just announced that he has sold out of his hedge fund's Valeant stock holding, a position that has cost the fund dearly.
Ackman's firm, Pershing Square Capital, invested in Valeant two years ago. Later that year, the drugmaker started to run into a spate of problems that wiped more than 90% off of its market value. Reuters estimated that the investment caused Ackman to suffer roughly $3 billion in losses. 
Pershing Square isn't the only hedge fund that had made a big bet on