La La Land (2016)

La La Land's ending devastates because it dares to show love as a casualty of ambition—Mia and Sebastian share a silent, tear-soaked smile that dissolves romance into reality. Chazelle's dream montage, which cost $2.3 million to film, reimagines their alternate life with wrenching visual detail. This bittersweet finale polarized audiences: 62% of Movieline readers in 2017 voted it the most heartbreaking ending of the decade, yet it also sparked intense debate about whether professional success is worth the cost—a question Grease (1978) avoids entirely by defaulting to fantasy.