Mary Warren exhibits courage and integrity when she comes to the court to recant her testimony about people she had previously accused of witchcraft. Of course, by the end of the act her courage falters and she goes back to her originial testimony.
John Hale exhibits it when he goes against Danforth and starts to argue that Abigail is really a liar.
John Proctor shows these things when he comes and confesses to his adultery with Abigail.
Giles Cory shows them when he refuses to tell wrote the affidavit he brought to the court. He knows that telling would get the person in trouble.