if I recorded you kicking a dog in the head in a public park, and posted it to TikTok without your consent, I’d be breaking the law?

Possibly, yeah. You have to make sure anything you release (here in Finland, as that's where I live) isn't "conducive to causing that person damage or suffering or subjecting that person to contempt", but what is or isn't is left a bit vague in the laws.

If there is enough backlash from a video like that against the person in the video, it can actually mean the courts see the defamation, loss of face, publicity or some other result as being enough of a punishment for the original crime and give them a reduced sentence or let them go. Say someone figures out who the dog kicker is, tracks them down and beats them up (or worse), contacts their job to get them fired or something like that for example. You are now partly responsible for that, and they just got a punishment that the courts will take into an account.

One of the most common that happens is shopkeepers releasing videos of people shoplifting (or worse, accusing them without being absolutely 100% sure), which has been multiple times proven to be illegal. You are free to send them to the cops, but you can't release them publicly.