Johnny is anything but cruel, unless you consider his breaking of a soda bottle to use as a weapon of defense as cruel. If anything, life has been cruel to Johnny! His drunken father beats him, and his unloving mother screams at him. Neither cares where he goes, who he is with, or what he is doing. His timidity is shown through his lack of speaking (which could be shyness) and his withdrawal from tense situations. His severe beating at the hands of a Soc gang has left him even more timid. His caring shows in his concern toward Ponyboy after he is jumped by a group of Socs and beaten up. Caring is something Johnny can do even though he has had little experience. It took a lot of nerve to stand up to Dally and keep him from harassing the Soc girls at the drive-in.
In The Outsiders, Johny Cade is the smallest and weakest member of the Greasers gang. I would say that timid and caring are his major character traits.
We can see that he is timid (or at least nervous) in two places at least. First, in Chapter 1, Pony describes him as having nervous eyes. Second, in Chapter 2, Pony and Johnny are talking to Cherry and Marcia. All Johnny can say is "hi," which he says shyly. Then he gets nervous and tries to just watch the movie.
You can see that he is caring from this same episode. That is where he stops Dally from harassing Cherry. This shows he cares about Cherry's feelings.