Technically violence is generally a criminal offence, at least in the UK. A criminal record will get you fired, be ineligible for many jobs, cause difficulties with insurance and so on.

There are extenuating circumstances, self-defence for example, but in the UK the law requires proportionality. However violence is usually a sign of someone who lacks control, humanity, a sense of proportion, reflects poorly on character and is not to be undertaken lightly. Habitual violence is of course abusive.

If someone harms your dog a reasonable and responsible adult would report the matter to the police rather than go for freelance reprisals.