<p>Online romantic and sexual rejection can elicit aggressive responses, yet few have explored how these reactions unfold in online contexts. This study presents a qualitative analysis of aggressive retaliation to online rejection. Among Canadian undergraduate student participants who had ever rejected someone online (<i>n</i> = 1701), 47.7% reported having experienced aggressive retaliation. Of cases where the sender’s gender was identifiable, 93% of senders were men. Notably, 67% of aggressive responses came from strangers, underscoring the role of low relational accountability. We analyzed open-ended narratives from participants (<i>n</i> = 812) who described a time they rejected someone online and perceived the response as aggressive or disproportionate. Using inductive thematic analysis, we identified four major themes: Disparagement (e.g., insults, name-calling), Harassment (e.g., obsessive messaging, unsolicited sexual content), Threats (e.g., blackmail, physical or sexual violence), and Rejection Dynamics (e.g., entitlement to consent, harm wishes, and contradictory insults). Our findings extend the online disinhibition effect by showing how anonymity and emotional distance can facilitate aggression. We also build on theories of moral disengagement and gender role strain to explain patterns such as entitlement and coercion. This study uniquely contributes to the literature by offering rich, inductively derived themes from a large qualitative dataset. Findings support targeted interventions, including educational campaigns on digital consent, platform-level moderation strategies, and automated messaging systems that respond to problematic behaviors. The open-access dataset also offers valuable material for future research and educational initiatives.</p>