We conduct a social dilemma experiment in which real-world leaders can punish group members as a third party. Despite facing an identical environment, leaders are found to take remarkably different punishment approaches. The different leader types revealed experimentally explain the relative success of groups in managing their forest commons. Leaders who emphasize equality and efficiency see positive forest outcomes. Antisocial leaders, who punish indiscriminately, see relatively negative forest outcomes. Our results highlight the importance of leaders in collective action, and more generally the idiosyncratic but powerful roles that leaders may play, leading to substantial variation in group cooperation outcomes. (JEL C93, D03, O13, Q23)