Blade Runner is a deep, deep movie.
Roy kills Sebastian even though Sebastian suffers from the same problem he suffers from.
Is Earth the off-limits Eden to the replicants?
There are layers upon layers in this movie.
I never understood that. One of the unanswered questions in the movie is "who is the bad guy"? Is it Deckard or Batty? But for the killing of Sebastian, I think you could make a very strong argument that Deckard is more of a bad guy than Batty.
That's why it's my favorite science fiction movie. I've seen it well over a dozen times and I can still watch and pick up on nuances or issues I'd never considered before. A true classic. Masterfully directed and despite being surrounded by a cast of really good actors, Ruter Hauer gives an absolutely haunting performance.