It is mentioned many times in The Vampire Diaries that after becoming a vampire your emotion gets heightened up, as in Elena's case her grief got heightened up and anger for a small interval. For Caroline it was a complete character change from insecure girl to confident mature girl. But what happened to the Salvatore Brothers after becoming vampires? Is it mentioned ever which of their emotions got heightened up?
Ok, So I was re-watching TVD and here's what got amped up for Stefan (S2,E3):
Caroline: And now you want me to eat bunnies, and I'm kind of freaking out, okay? - Now you're laughing at me.
Stefan : No, I'm not laughing. None of this is funny, trust me. It's, heh It's just that, uh -
Stefan : When someone becomes a vampire all of their natural behaviors get sort of, uh, uh, amplified.
Caroline : What do you mean?
Stefan : I mean, as a human, I cared deeply for people and how they felt. If they were hurting, I felt their pain. And I felt guilty if I caused it. And, uh, as a vampire, all of that got magnified.
Oh and to answer your question (since you asked which brother), every vampire's emotions/traits get heightened. So its not just a particular vampire. Both Damon and Stefan each get one trait amplified. Will add info on Damon if I recall it. Or maybe someone can add it here if they know it.