If we're admitting double arias into this discussion, my choice would be
"La ci darem la mano" (from *Don Giovanni*), the most convincing seduction
scene I've heard on opera.  Aside from the beautiful music, there's the
tantalizing text of Zerlina's responses to the Don's blandishments ("vorrei
e non vorrei, mi trema un poco il cor", "mi fa pieta Mazzeto", "presto non
son piu forte") almost resolving itself in the "andiam, andiam mio bene, a
ristorar le pene d'un innocente [sic] amor" but for the timely arrival and
intervention of Donna Elvira.

Walter Meyer