Controversial marketing involves strategies that provoke debate and strong reactions, aiming to create memorable impressions while risking backlash and brand damage. Notable case studies include H&M's racially insensitive campaign, KFC's humorous crisis management, Dove's diversity promotion, and Zomato's culturally insensitive advertising. Key learnings emphasize the importance of audience sensitivity, effective crisis management, and the need for a balance between boldness and cultural awareness.