I notice the question is "in fantasy and science fiction", not "in fantasy and science fiction
literature" - which leaves me free to mention Kain, of Legacy of Kain.
Kain is complex and conflicted, with perception of him vacillating between arrogant tyrant and altruistic martyr at various times. He has a significant arc of development, and his motivations and moral codes are fascinating to me. Add to this his acerbic and mocking sense of humour, and I find Kain surprisingly engaging.
Plus, he is voiced by the incomparable Simon Templeman, and this is what elevates the good dialogue to true greatness. I would love to see (or hear) Simon Templeman perform Shakespeare.
Kain wrote:This one reckless act unravels the skein of history. The Nemesis never becomes the Nemesis; William dies a martyred saint. I, the vampire assassin, become author of my own species' extinction - and Moebius profits from all of it.
Kain wrote:When I first stole into this chamber centuries ago, I did not fathom the true power of knowledge. To know the future, Raziel; to see its paths and streams tracing out into the infinite... As a man, I could never have contained such forbidden truths. But each of us is so much more than we once were...
And perhaps my favourite (certainly the one I find easiest to recall, and most flexible for everyday use):
Kain wrote:The town of Steinchencroe bore with it the infamous aroma of its inhabitants. In life, I would not have graced the place with my presence; in death, I merely added to the stench.