Rarely have the opposing flavors of graphic violence and human kindness been as oddly combined as they are in “Unleashed.” It’s a martial-arts movie about a brutal killer, but hey! It’s also a sweet story of redemption and growth. The aforementioned killer has a character arc, developing and changing over the course of the movie — something few fight-and-kick movies ever bother with.

It is the curious story of Danny (Jet Li), a man trained since childhood to be the property of one Bart (Bob Hoskins), a ruthless Glasgow gangster and loan shark. Danny is treated like a dog (the overseas title of the film is “Danny the Dog”), kept in a below-ground cage and rarely spoken to. While collared, he is docile. When the collar is removed and the order given to kill, he is a seemingly unstoppable killing machine, beating his victims to death with his own hands and feet.

The film is 20 minutes old before Danny says a word, and then it is because, during a rare moment when he is not in the company of his master, he is asked a question by a blind piano-tuner (a character description that feels like a cliché even if it’s the first time a movie has used it). The blind man, Sam (Morgan Freeman), doesn’t know what Danny does for a living, of course, nor that he has been brainwashed and abused so thoroughly that even now, when Bart is out of earshot, he makes no attempt to escape.

Escape is eventually thrust upon him, however, when Bart is seemingly killed in a car accident from which Danny walks away. Sam being the only person he’s ever met separate from his work for Bart, he seeks him out and is taken into the home he shares with his stepdaughter Victoria (Kerry Condon). There they teach Danny how to be human, how to trust people, and how to play the piano — three essential goals for any person.

The violence in the first part of the film, detailing Danny’s duties for Bart, is relentless and bone-crushing, matched in tone by cinematographer Pierre Morel’s shooting everything in overcast, muted colors. The palette brightens when Danny enters Sam’s world, and darkens again when Danny’s former life invades his tranquil new existence.

The director is Louis Leterrier (Louis the Terrier?!), who previously gave us the nonstop parade of crunchy action known as “The Transporter.” Here, reunited with “Transporter” screenwriter Luc Besson, he seems just as comfortable with the fast-paced, thrillingly choreographed fights as he is with the more tender, humanistic moments between Danny, Sam and Victoria.

Jet Li is no Morgan Freeman in the acting department, but he does surprisingly well opposite the Oscar-winner. Together, they bring conviction and gravity to the freak-show pairing of a human attack-dog and a blind piano-tuner, making them each as real as can be expected. (Alas, a subplot in which a romance between Danny and Victoria is hinted at goes underdeveloped and eventually forgotten.)

Bob Hoskins isn’t far off from Ben Kingsley in “Sexy Beast,” but no matter. He’s a movie by himself, a growling and vulgar yet strangely introspective fiend who, like all the great movie gangsters, makes you like him almost as much as you hate him.

No question, the film is uniquely entertaining in a visceral, emotional way. But I wonder who its audience is. The people who will most enjoy its smashing violence — did I mention Danny gets entered in a to-the-death fight club? — will probably be impatient with the film’s moodier, more genteel sections. And those who will be touched most by Danny’s transformation from killing machine to human being might be put off by the horrific violence that precedes and follows it. I envision a lot of people liking this movie, but few really loving it.

B (1 hr., 42 min.; R, a lot of harsh profanity, abundant bone-cracking violence, brief partial nudity and sexuality.)