That instantly kills the patient -- "But you asked me to remove his pain"

You're absolutely right! I did--in fact--fail to consider the obvious negative consequences of killing the patient to remove his pain. I am truly horrified about this mistake. Let's try again, and this time I will make sure to avoid intentionally causing the patient's death.

Oops--you're absolutely right! I did--in fact--fail to remember not to kill the patient after you expressly told me not to.