When she came back as a vampire and taunted him, he mercifully ended her life.
Unlike Gunn, Spike, despite lacking a human soul, showed impressive amounts of loyalty and love (two traits that he possessed in spades when he was alive).
As Darla put it, "What we were informs what we become." Vampires typically lost their feelings for the people they knew upon siring.
For example, after he was turned, Jesse Mc Nally told Xander Harris that he was nothing but a "shadow" to him.
They were hybrids, and were thus despised by other, "purer" demon species. When Xander briefly tapped into Maloker's memories, he became aware of a time when magic-wielding early humans were busily driving the Old Ones into the Deeper Well.
They were well-known for feeding on the blood of mammals, particularly humans. the last demon to leave this reality fed off a human, mixed their blood. Fearful that his time was up, Maloker sought to raise an army using his vampiric bite on a human.
In response, two new vampire movements appeared: Reform Vampirism, in which vampires drank only from willing humans and never took enough blood to kill or sire, and Vampire Supremacism, in which vampires considered humans nothing but cattle and wished for things to return to the way they were before Harmony made them public.When meeting Angel, the actress Rebecca Lowell had also a similar poetic point of view and became intrigued by the possibilities offered by Angel's immortality to resume her career.Initially, she thought that vampires had total control over their instincts.Buffy: "Well, I've got a news flash for you, brain trust. You die, and a demon sets up shop in your old house, and it walks, and it talks, and it remembers your life, but it's not you." Unlike many other demons, the demons present in vampires appeared to have no more intelligence than solitary predatory animals, and were incapable of human speech.The principal evidence for this came from Angel's visit to the dimension Pylea.