Lance Armstrong for Nike "Livestrong"

Nike’s Livestrong campaign became the costliest endorsement collapse in sports history. When Lance Armstrong’s systematic doping was exposed in 2012, Nike severed ties and wrote off $24 million in unsold merchandise, a loss that outperforms #2 Tom Brady’s FTX fallout in sheer financial impact. The partnership, once hailed as a charity model, crumbled faster than any other on this list, with 90% of Livestrong sales dropping within months. Armstrong’s betrayal cost the brand not just money but consumer trust, a data point that underscores how deeply a single athlete’s deception can wound a global icon.