Romelu Lukaku — Inter Milan to Chelsea (2021) — £97.5 million

Romelu Lukaku's £97.5 million return to Chelsea in August 2021 — from Inter Milan, where he had been Serie A top scorer and won the league title — lasted 12 months before he gave an explosive interview to Italian TV saying he "never wanted to leave Inter" and that "the Chelsea transfer was wrong." He was loaned back to Inter the following summer. The deal is widely studied as one of football's most spectacular transfer failures: a world-class player at his peak, a Premier League club with unlimited resources, and zero chemistry between the two parties.