I think what should be noted first about Pacino performance is the daring nature of it. Sonny is a completely original creation, that is not like any other performance he gave before this. Pacino does a very distinct higher voice, that is frankly a masterstroke in his performance. His voice just works so incredibly well for the film, and it as well really shows that Sonny is a very particular man with a rather particular history.
Al Pacino begins the entire film brilliantly and never stops being so for the entire film. His opening moments of his performance, are some of the best moments of any performance ever. Sonny begins is robbery quite incompetently, rushing too much, not even knowing that all his partners in crime are fully with him, or knowing that the right amount of money will actually be in the bank.
Pacino through this whole first long scene is outstanding, as rushes through his effort, Pacino is perfect in Sonny's uneasiness as he tries to get the job right, but continually faces problem. Even just pulling his gun out of its box it was concealed in is troublesome for him, Pacino is great in just the simple act of Sonny messing up pulling the gun out of the box showing his inexperience, nervousness, haphazardness, as well as manic way of Sonny, in just this small action, and at the same time as well is able to be appropriately humorous in just the natural way of Sonny.
Pacino through his whole process of failure is fascinating to watch, and it only gets better he truly fails as a bank robber when he gets trapped inside of the bank due to the police waiting on the outside. He is amazing in just his single moment of realization of his situation now, as he sits on the floor. Pacino clearly shows how much is going through Sonny's head at this single moment, and he may even up show his similar scene in the Godfather, which I find is about as high of praise as I possibly can give.
In these whole early scenes, that are technically more action based than technically dramatic based, Pacino manages to already turn Sonny into a fully realized three dimensional character. Pacino shows that Sonny is a rather on his last straw sort of fellow, he wants to be organized, but fails to be, and but also suggests that Sonny is not sure of himself, or his claims of violent ability, a particularly strong moment is when his bank robber partner Sal (John Cazale), asks if Sonny really will be able to carry out his threat of throwing bodies at the door, Pacino is perfect in his reaction making properly clear that the situation is a bit over Sonny's head.
When Sonny finally faces the music, so to speak, and finally begins to challenge the police how well Pacino excels in a great variety of ways with his performance. When finally coming out Pacino is again incredible in the way he portrays the entire scene, and every scene of this type with the Police, especially the first one where he plays to the entire crowd. Pacino still shows that Sonny is no genius by any means but shows that Sonny due to being backed in the corner is trying to use every idea he has.
Pacino controls each of these scenes incredibly well. He does not do as some sort of commanding General, but a man who has never had any actual power, he is not at all that good at it, but he tries his best. Pacino is just great in how he shows Sonny is playing it extremely safe always being hesitant in some way, being afraid of being killed really, how he really always has to almost jump ahead of himself to cut off the police when they want to try to pull a fast one, it is amazing to watch, the Attica outburst, which plays to the rowdy civilian crowd, by Sonny is not some brilliant calculated move, but rather a small man using whatever he can do get out of his situation which is basically being between a rock and a hard place.
Now this would already be frankly by an incomparable achievement if the performance stayed the same through the rest of the film, but it doesn't as we learn more about Sonny, and as Sonny situation continues on. Sonny turns out to have a homosexual relationship with Leon (Chris Sarandon) a preoperative transsexual, their phone call together is a pivotal moment for Pacino's performance. It is an amazing moment, showing his history with Leon, that Pacino subtly suggests brings out another side of Sonny, that has almost a poignancy to it, a simply astonishing.
As his negotiation becomes more difficult, Pacino is brilliant in showing both Sonny's mental and physical disintegration. Physical in showing he is having a harder time, despite still working hard with every move by his opponents, as well as the fact of bearing the heat and the time of the day. Mentally by him facing the facts of his rather difficult life. His trouble with both of his wives that he has, as well as his problems with his mother, and just his entire present state. Pacino shows that everything is deeply weighing on Sonny.
Pacino never stops being incredible with his heartfelt moment where he sees his possible fate at the end of the day, and attempt to dictate his will, well still comprehending his situation. Also his last moment, that truly shows where the day has brought him, and it is a stunning powerful silent moment as he sees what he has done has lead him. Pacino keeps his energy, as well as the tremendous power of his performance through the entire performance it never does end, Pacino never has a boring or a false moment. He is incredible throughout and in fact he always presents even more of Sonny, as well as holding every moment he is on screen. This is simply a truly great, and amazing performance that stands firmly as one of the best performance given by an actor, period.
