Sam Winchester

Though Sam is usually kind, empathetic, intelligent and independent; he can also be arrogant and stubborn. He is often the exasperated voice of reason in his relationship with Dean, who in turn sees him as exaggeratedly prissy and teasingly calls him "bitch". Dean actually has respect for Sam as a hunter and trusts Sam to "have his six". Sam shows some obsessive-compulsive tendencies, such as the desire to be in control of his situation and being fastidious about cleanliness and order. He does not seem to drink alcohol as much as Dean does and has a much healthier diet than his brother (Dean himself scoffs at Sam's diet and calls it "rabbit food"). Sam also has a severe phobia of clowns, due to his brother often leaving him at Plucky Pennywhistle's Magical Menagerie when they were children. This is not helped by the fact that every time they have encountered a clown in the show, it has tried to kill them.

Because of his intelligence, Sam is usually assigned the role of researching information for hunts; he is the "brain", whilst Dean is the "muscle". He normally remembers details that Dean overlooks and is prone to make connections quicker than his brother. He also knows a great deal of information that causes Dean to label him a "walking encyclopedia of weirdness". In college, Sam scored a 174 out of 180 on his LSAT, which Jessica noted was "scary good" in the series pilot. In spite of their bickering, Sam has looked up to Dean since they were children and knows him better than anyone else.

He tries to get Dean to open up about his emotions and problems, and encourages him to take care of himself; on several occasions, he has even been frustrated by his brother's fixation on placing Sam's well-being above his own. However, Sam shows similar protective tendencies towards Dean, particularly after Dean makes his deal and returns from Hell as a shadow of who he used to be, to the point that Sam's memories of Dean allowed him to regain control of his body while possessed by Lucifer. Sam tends to be driven by feelings of anger and vengeance.

Sam became determined not to let Dean down again and took on the weight of the trials to prove himself. They took an extreme toll on his health, and as Sam got sicker, he became ever more defensive of Dean's attempts to mother him. He eventually got to the point where he was so ashamed of letting his brother down that he was willing to commit suicide in order to finish the trials. Dean managed to talk him back from the edge, but they weren't able to cure Sam before he succumbed to the effects.