Cristiano Ronaldo — Real Madrid to Juventus (2018) — €117 million

Cristiano Ronaldo's €117 million transfer from Real Madrid to Juventus in July 2018, at age 33, was widely considered a footballing earthquake. He had won four Champions League titles in five years at Madrid. He won two Serie A titles at Juventus but never delivered the Champions League they had bought him for — losing in the quarterfinal to Porto in 2021. He returned to Manchester United in 2021 before joining Al Nassr for €200 million per year in 2023. His Juventus spell remains the most analysed case study in the diminishing returns of late-career superstar transfers.