How does Dickens contrast the convict and Pip?

This happens gradually through the book. They actually begin to be more like each other as the book goes on.

Pip is depicted as a "small bundle of shivers growing afraid...and beginning to cry." He is portrayed as a helpless, frightened innocent. The convict, on the other hand, is "a fearful man" who "glare(s) and growl(s)." He is a rough, malevolent and threatening man

Both pip and the convict have good hearts. Pip merely has his own prejudices against Magwich. This isn't to say Magwich is without fault, he's just more sincere. Pip takes awhile to attain that sincerity.