Does power increase a person’s tendency to punish or forgive norm violators? Given that existing studies report mixed findings, we examined whether power contributes to both, as a function of person and situation. In four studies employing various designs, we tested the prediction that power facilitates the circumstantially dominant response, either punishment or forgiveness, determined by the person’s dispositional trait or a contextual cue (e.g., apology). In Study 1, high chronic power predicted stronger punitive attitudes toward a criminal perpetrator, especially if one is unforgiving by nature, while it also predicted forgiveness when people envisioned the perpetrator being repentant. Study 2 further confirmed the pattern with a simulated workplace scenario where we manipulated people’s experience of power and the absence/presence of an apology. In Studies 3 and 4, we tested the prediction using different indicators of aggressive behaviour. People primed with high power exhibited greater aggression toward an unapologetic target and lesser aggression toward an apologetic target, and this effect was especially salient among people who held a strong belief about justice. Reconciling mixed findings of existing literature, the results highlight how an interplay of power and other factors systematically determines people’s decisions and actions in cases of conflict.