Zest for Life
Roy Batty might be the movie's most compelling character. He's a Nexus 6 replicant—in other words, a manufactured human—who has escaped from slavery on distant colonies in outer space, and his quest is to obtain more life, to override the predetermined four-year lifespan that his corporate creators have given him and other replicants.
Roy begins this quest by heading to the lab of Hannibal Chew, the genetic designer who created Roy's own eyes. Chew provides him with the next step on his journey: find J. F. Sebastian, another designer, who will then be able to lead Roy to Dr. Eldon Tyrell, the man who basically created him. Roy follows through, forcing Sebastian to take him to Tyrell's place. When he arrives, he confronts his own creator—a twisted version of his father figure.
They have the following exchange:
TYRELL:What..? What seems to be the problem?
TYRELL: Death. Well, I'm afraid that's a little out of my jurisdiction, you...
ROY: I want more life, f***er.
Um, yeah, this meeting is a bit contentious, you might say—even more so after Roy gouges Tyrell's eyes and crushes his skull. Why does he do that? Well, Tyrell has just told him that there's no way to extend his life. Roy goes ahead and kills Sebastian, as well, though this happens off screen.
All of this gives us the impression that Roy—although he's been seriously wronged by his society—isn't on too even a keel. He seems somewhat crazy and definitely violent. (Also, it's noted that he and the other replicants killed all the crew-members and passengers on the space shuttle they hijacked to get to earth… so there's that to keep in mind.)
Tearjerker Bad Boy
But the movie concludes by upending our whole impression of Roy. While he chases Deckard around J. F. Sebastian's old apartment building, it seems like Roy's going to kill Deckard—after all, Deck just murdered Roy's girlfriend, Pris. And he does break two of Deckard's fingers. But, surprisingly, when Roy finally has the chance to kill him, he prevents Deckard from falling off a building and saves his life. Realizing that his own life is coming to an end—the four-year time limit is just about up—Roy has a moment of wonder, compassion, and grace. Before dying, he says:
I've seen things you people wouldn't believe. Attack ships on fire off the shoulder of Orion. I've watched c-beams glitter in the dark near the Tannhäuser Gate. All those ... moments will be lost in time, like tears... in rain. Time to die.
Deckard goes from being a classic rebel trying to take down his creator—like Prometheus or John Milton's Satan—to a Christ-like figure, who reacts to his own suffering with mercy and love. We're not making this up—the Jesus imagery is pretty overt: Roy drives a nail into his own hand in the last moments of the film. He then releases a dove, apparently symbolizing his soul, which soars upward as he dies.
That's the paradox of Roy's being: his society considers him to be just a biological machine, but he manages to prove that he's more truly human than many of the other characters in the film, affirming his humanity through suffering before releasing a dove that symbolizes the soul he isn't supposed to even have.