Atormenta comes from the verb atormentar, meaning 'to torment' or 'to plague'. It's a strong, evocative word that conveys deep emotional distress.
In "Cuando Volverás", the singer uses atormenta to express the intense pain and anguish he feels at the thought of his beloved being with someone else: "Y el pensar que estás con otro me atormenta cada día más" (And the thought that you are with another torments me more each day). This word perfectly captures the song's theme of heartbreak and longing.
"Cuándo Volverás" is Aventura's bachata plea to a girlfriend who walked out with no warning. She left one morning without a note, without any sign of where she went, and the narrator is left asking, over and over, when she'll come back.
He admits he doesn't deserve what happened to him. He can't eat, he can't sleep, he just waits. The chorus keeps circling the same two questions: "when will you return?" and "why are you doing this to me?" He still loves her completely and begs her to come home.
Throughout the song he calls her "morena," an affectionate nickname for a woman with dark hair or a tan complexion, common in bachata and across the Spanish-speaking Caribbean.