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Valeant Pharma (VRX) is the easy answer.
Bill Ackman's Pershing Square Holdings (PSH) is now down 19% year-to-date after being down 7.3% in October. Valeant is a big contributor to that, with the stock off 40% for the last month and down 50% since Ackman went active.
With the fall, it's moved from his second largest long-only U.S. holding to fifth.
The other major detractor has been his SPAC, Platform Specialty Products (PAH), down 17% over the last month.
He still owns 5.7% of VRX and 20% of PAH. PAH is off 55% since Ackman went active in 2014.