I'll never forget the experience of seeing Tosca at the MET. Tosca is one of the great operas of all-time, but it has all the subtlety of an eight-year-old with a squirt gun. When the villain Scarpia entered for the first time, the orchestra suddenly let out four enormous dissonant chords. I leaned over to my friend and whispered to her "I think he's the villain..."
Scarpia is the chief of Napoleon's Secret Police in Rome, and he is opera's most larger-than-life character since Don Giovanni. Scarpia uses his position to achieve two goals: to terrorize the populace of Rome, and to sleep with every beautiful woman in this sexiest of world cities. The music that follows him when he enters the stage inspires not only terror but also that this is a supremely charismatic man in love with the hatred that he inspires.
So when he comes to the Church of San Andrea Della Vallea to arrest the painter Mario Cavaradossi, he is not only doing it because Cavaradossi is an avowed republican, but also because Cavaradossi has the best-looking girlfriend in town - the actress Floria Tosca. And simultaneous to the Te Deum service, Scarpia sings about how he will arrest and murder Cavaradossi, and use his position to extract favors from Tosca through false promises to have Cavaradossi released. All ending with the famous line "Tosca, you make me forget my god." After that line, my friend leaned over to me and whispered "Wow, he's eeeeeevil!"
No offense to Ruggiero Raimondi, who is one of the great Scarpias. But the clip from below is even better, albeit with no translation. This is the all-time champion Scarpia, Tito Gobbi, singing the same piece. Only in this version, Gobbi knows the real secret, which is that Scarpia is not just a slimy dignitary, he's a Mephistophelean figure who gets off on affronting God. Raimondi is great, Gobbi is unforgettable. Don't skip the first few minutes either, even if you don't know French (mine certainly isn't good enough to understand everything being said here). It shows just how dramatically Gobbi transforms himself into character.