Digitalization has changed the ways consumers interact with brands and has led to increasingly empowered consumer markets, where some consumers engage in activities that deliberately try to harm a brand. Against this background, this dissertation introduces a conceptual framework of aggressive consumer behavior toward brands and examines the antecedents leading to such behavior, its outcomes, and how managers can respond to diminish its damage. Paper 1 (Kähr et al. 2016) introduces the phenomenon of consumer brand sabotage (CBS) as a form of hostile aggression and develops a conceptual framework of aggressive consumer behavior toward brands. It explains the psychological mechanisms leading to such aggressive behavior and distinguishes between instrumental and hostile aggression. Manuscript 2 examines the brand damage of CBS as a form of hostile aggression. It studies whether, when, and how a CBS activity affects other observing individuals. Finally, Manuscript 3 investigates how a company should respond to negative electronic word-of-mouth as a form of instrumental aggression depending on its credibility.