I love Scarface, so this was a tough one. Pacino's done so many great flicks. I'd have to say, though, as far as which of these best expressed his acting/artistic ability, it's Scent of a Woman. "The colonel" was so real you could feel his bitterness, as well as his no-nonsense attitude. Plus it had a great ending.

"Vaya con Dios, Castle. Go with God."
"God's going to sit this one out." The Punisher (2004)