We are not supplied with that much information about Bob in this excellent novel. However we are told that he is handsome, wealthy, and most importantly, a Soc. He is Cherry's boyfriend, and it is clear that he likes to drink, but that this causes problems in his relationship with Cherry. Note what she says to him in Chapter 3:
"Bob, I told you, I'm never going out with you while you're drinking, and I mean it. Too many things could happen while your're drunk.. It's me or the booze."
However, it is also strongly indicated that it was Bob and his gang that was responsible for Johnny's attack that has left him so traumatised. Note what Ponyboy sees as the car pulls up:
Johnny was breathing heavily and I noticed he was staring at the Soc's hand. He was wearing three heavy rings. I looked quickly at Johnny, an idea dawning on me. I remembered that it was a blue Mustang that had pulled up beside the vacant lot and that Johnny's face had been cut up by someone wearing rings...
So, clearly Bob has a violent side to him that, when unleashed, could be incredibly destructive. However, as Cherry tells Ponyboy later on, it would be wrong to label him as a violent psychopath alone:
"You only knew his bad side. He could be sweet sometimes, and friendly... Bob was something special. He wasn't just any boy. He had something that made people follow him, something that marked him different, maybe a little better, than the crowd."
It is important that the author presents Bob as just human like everyone else in the play. He is another character that would benefit from looking at sunsets, and another young man caught up in a system beyond his understanding and control. So whilst we are perhaps tempted to think of Bob in purely negative terms, it is important to maintain a balanced view of his character.