Scientists have noted the song’s use of "appoggiaturas"—ornamental notes that clash with the melody to create tension before resolving. This musical "clash" triggers a physical emotional response in listeners.
She co-wrote the track with Dan Wilson (of Semisonic), who also played the iconic piano accompaniment. Why It Makes You Cry: The Science Adele - Someone Like You
The song’s global dominance was largely fueled by a single, legendary performance. Someone Like You (song) | Adele Wiki | Fandom Adele - Someone Like You
Adele wrote the song to come to terms with the end of her first "real" relationship. A few months after they split, her ex was already engaged to someone else. Adele - Someone Like You
There is a psychological reason "Someone Like You" is so effective at inducing tears.