One of those monsters that is at the same level of Robert De Niro. That is like saying he is among the best of the best.
Taking into account the movies I've seen lately with Al Pacino that I had yet to watch (Donnie Brasco, Carlito's Way, Dog Day, Scent of a Woman, etc) it is clear to me now, I consider him the most talented actor I've seen on screen.
"Say hello to my little friend!"
Give this one a look as well:
http://www.listal.com/list/actor-robert-de-niro-7534