On iPhones, three ways to get rid of the keychain data of an app 1. wipe the phone AND you must not restore backups 2. jailbreak the phone 3. the app can wipes

On iPhones, three ways to get rid of the keychain data of an app 1. wipe the phone AND you must not restore backups 2. jailbreak the phone 3. the app can wipes its own keychain (but apps don’t expose this feature generally)