Feldman’s success could hinge on One Mad.

The foreclosed, lawsuit-laden, incomplete tower that stands at One Madison Avenue scared away most of New York City’s big-name developers, except for Bruce Eichner, who reportedly placed a low-ball $45 million bid. So it came as quite a surprise last month, the Observer said, when a man intent on rising to those ranks agreed to pay $165 million to acquire the Flatiron tower. That man is Ziel Feldman, and it’s one of several risky bets the head of HFZ Capital is making in the midst of a market recovery. It started during the boom, when Feldman successfully refurbished a pre-war condo at 823 Park Avenue, and sold units for more than $2,000 per square foot. But a Park Avenue condo is one thing, the “collapsed crane tower” at East 51st Street, the Setai condo conversion downtown, and One Madison Park are far more risky, and could determine whether Feldman ultimately becomes a leading developer or another in a long line of failed risk-takers. Sources told the Observer that after the lawsuits are settled and construction is finished, Feldman would need to get $2,500 per square foot, on average, to make a profit.