From Holocaust Survivor to Fugitive
Roman Polanski was one of the biggest young directors in Hollywood in the late 60s and early 70s. After surviving the Holocaust as a boy (his mother was killed by the Nazis), Polanski became an up-and-coming director in Poland before striking out for the U.S.
His first major success was the 1967 horror movie, Rosemary's Baby—the suspense-driven Godmother of all the other Satanist/exorcist/devil-baby thrillers, like The Omen and The Exorcist.
Then, tragedy struck in the craziest way possible: members of Charles Manson's cult murdered Polanski's pregnant wife, the actress Sharon Tate (this became the subject of the classic true crime book Helter Skelter). He was shattered, but eventually returned to L.A. in 1974 to make Chinatown, which is almost universally acknowledged as his masterpiece.
Yet, this story of tragedy and triumph has a major twist…
In 1977, Polanski raped a 13 year-old girl in Los Angeles (allegedly, but he admitted to having sex with her, which is statutory rape). He initially contested the charges before pleading guilty to one charge, that of unlawful sexual intercourse with a minor. But the legal process wound on, and, eventually, Polanski fled the country and ran away to France, where he's been living ever since.
Earlier in Polanski's career, everyone essentially said, "This guy survived the Holocaust only to have his pregnant wife killed by Charles Manson's gang. We should feel bad for him."
But then, after news of the rape broke, public opinion decidedly turned against him, with the public thinking that Roman Polanski's life was turning into a Roman Polanski movie. And people have been arguing about Polanski and his reputation as a filmmaker ever since.
So, the point is: the dude's controversial. (Source)
Craftsman with Some Dark Places
Polanski says that he treats being a director just like a job—he just tries to select good screenplays and make them into artfully crafted movies. This implies it's not all that personal, but we can definitely see themes that link his films. (Source)
Despite this "it's just a job" stuff, he gravitates towards making certain kinds of movies that suit his style—particularly dark and disturbing movies. Many of his movies involve sinister conspiracies with a hero or heroine trapped at the center.
Chinatown is a good example, since the hero and heroine are both ultimately overwhelmed and vanquished when they come up against the water-theft conspiracy. The same goes for Rosemary's Baby and the more recent The Ghost Writer. In the first, a young woman gets caught in a satanic conspiracy, and in the latter, a British prime minister's ghostwriter starts to uncover some disturbing secrets that expose…another conspiracy.
Themes of persecution and confusion and injustice run throughout all of his works—like his true story Holocaust film, The Pianist, and his adaptation of Thomas Hardy's Tess of the D'Urbervilles.
We can see that in Chinatown too, obviously. The bad guys are going to keep stealing water, Noah Cross is going to take possession of his daughter/granddaughter…and there's nothing Jake Gittes can do about it anymore.
Whatever you think about Polanski, it's hard to deny that he possesses genius for exploring the dark side of human nature, and the seedy underbelly of the psyche.