Harry Potter and the Prisoner of Azkaban
"Harry [...] I as good as killed them," he croaked. "I persuaded Lily and James to change to Peter at the last moment, persuaded them to use him as their Secret-Keeper instead of me [...] I'm to blame, I know it [...]" (19.72)
"How dare you," he growled, sounding suddenly like the bear-sized dog he had been. "I, a spy for Voldemort? When did I ever sneak around people who were stronger and more powerful than myself?" (19.107)
"He – he was taking over everywhere!" gasped Pettigrew. "Wh- what was there to be gained by refusing him?"
"What was there to be gained by fighting the most evil wizard that has ever existed?" said Black, with a terrible fury in his face. "Only innocent lives, Peter!" (19.162-3)