It's no secret Robert De Niro has fallen on hard times in recent years, especially insofar as "hard times" are defined as "choosing to appear in terrible movies almost exclusively." But he's played several iconic characters in the past, including Al Capone in Brian De Palma's The Untouchables.
This film has many famous scenes. Here's one of my favorites, in which Capone has a friendly meeting with his associates, discusses his love of baseball, and then hits a line drive up the middle. His speech leading up to it is great ("Enthusiasms... enthusiasms... enthusiasms"), and the tension is unbearable -- especially if, say, you first watched this movie years ago and know how the scene will end but don't remember exactly when it's going to happen.
The scene is based on a legend about Al Capone that may or may not be true. Albert Anselmi, John Scalise, and Joseph Giunta were found dead in May 1929, all of them shot and horrifically beaten. Years later, the story would emerge that they'd been lured to a dinner by Capone (they were all associates of his), who had turned on them with a baseball bat before other Capone henchmen stepped in to finish the job. I don't know if it's true, but I like to think it is.
By the way, while the violence here isn't as explicit as I remembered it, it's still pretty harsh. It might be considered "not safe for work" if you work in a place where the bludgeoning of ineffective team members is frowned upon.