How does Hollywood make the act of revenge justified?

If you do not know the answer please direct me with a link to a site that does, thanks.How does Hollywood make the act of revenge justified?It's common sense really, not sites. Basically you need to see these revenge-type films and make notes on similar traits. I'll help you by saying the film (or more specifically, writer and director) tries to make you sympathise with the character, and this may result in something like a loved one of the protagonist is murdered, and the killer gets away. Sometimes the law may not be useful/ is corrupt, and so the 'hero' of the piece sets off to hunt down the killer as a means of justice and retribution.