But even if you should suffer for righteousness' sake, you are blessed. "Don't fear what they fear, neither be troubled."
even if -- Peter is writing to Christians already suffering for their faith, therefore he is not saying that such suffering is improbable. His point is that no one will ultimately or finally harm Christians, “even if” they suffer now, for God will reward them (cf. Romans 8:31). Indeed, they will be blessed by God in their sufferings (cf. Matthew 5:10)