Which term describes a situation where someone plans to do the wrong thing and succeeds?

The term that accurately describes a situation where someone plans to do the wrong thing and succeeds is a mistake. A mistake typically involves an intentional decision that leads to an unfavorable outcome, whereas the individual had knowledge of their actions and chose to proceed anyway. This distinguishes it from other terms, such as a slip, which often refers to an unintentional error or oversight; an accident, which generally describes an unintended event that occurs without prior planning; and failure, which denotes a lack of success but does not necessarily involve an intent to do wrong. Knowing this context helps illuminate why "mistake" is the most appropriate choice, as it encapsulates both the intent and the achievement of an undesired outcome.