Think of someone real or fictional whom some people regard as a "hero" for helping others, stopping something bad or evil, and so forth, even though by doing so they violated what would normally be considered a moral rule (focus on morality; don't simply think of someone who broke the law).
For example, they may have lied, broken a promise, stolen, harmed someone innocent, or even murdered, but done so with good intentions.
(Note: this last part is crucial: make sure you explain what it was that they did that would otherwise be morally questionable. Also, it need not be someone you think is a hero.)
600 word count required