MBTI Type: ISTP
He has a very logical approach to life, though somewhat twisted; he tests the Slayer to find out what she is made of, before attacking her. He assigns other vampires to record her techniques so he can learn her weak spots and usual moves. He quickly sizes up people, situations, and possibilities and chooses one, without feeling the need to explain his actions, but they are often logical in some way (like, killing off the brat kid vampire and taking over). His decision to go to hell and back for a soul is not for his own gratification but because he earnestly wants to change so that Buffy will love him. Spike has a hot temper that flares up under stress and causes him to vent endlessly his feelings (he confides in Willow while holding her hostage, and asks her for relationship advice). Spike talks through his feelings and wears them openly, but also de-emphasizes them, which means he sneers at Angel’s attempts to atone for his many mistakes. “I had a plan,” he says. “It was a good plan. Smart. But I just got so bored!” This happens a lot. Spike sizes up situations and leaps into them. He is opportunistic, can pull a smart-ass remark out of midair, and inclined to not think through all his decisions. He has zero appreciation for “how things are done” (“I’m not sentimental”) but instead prefers to make his own way in life. He enjoys sensual pleasures and his time spent with Buffy, whether that involves physical violence or sexual pleasure. He is good at instinctively reading people, sensing their true intentions or possibilities, and figuring out how to exploit them. Spike also has a rich inner world, which as a human he used to express through poetry but now he keeps it locked away. His gut feelings are often good, but he sometimes ignores them in favor of immediate gratification. Angel says that once Spike fixates on something, he will not stop until he accomplishes it… or destroys it.
Enneagram: 7w8 sx/sp 
Spike does not have a long attention span; he comes up with a great plan, then gets bored, and goes on impulse instead. He moves from one thing to another with reckless abandon, running away from his fears with “distractions” (drinking, eating people, and sex). He is full of witty jokes and banter intended to get a rise out of other people and/or amuse himself. Nothing is serious to him and he enjoys relentlessly mocking Angel, especially when he temporarily turns into a puppet. Spike can be easily distractible and impulsive, but also can sacrifice his needs and wants for Drusilla (and later, Buffy). He has a low-key desire to be included, it just doesn’t run his life. He can be harsh and judgmental under stress, but rarely lingers there, since his 8 wing isn’t about to put up with any nonsense. He likes to push people’s buttons and takes some sadistic pleasure in having dominated (killed) several slayers. Rather than live under the leadership of a child vampire, Spike sets him on fire and takes over.