Final answer:
The principle that requires the removal of existing harm is nonmaleficence.
Step-by-step explanation:
The principle that requires the removal of existing harm is nonmaleficence. Nonmaleficence is the ethical principle that states that we should act in ways that do not cause harm to others. This principle is commonly used in clinical settings to ensure that patients are not unnecessarily harmed during medical procedures or treatments. Nonmaleficence also applies to research trials, where it is important to design trials in a way that limits harm to participants as much as possible.