It's indeed hard to say as there are many ways and it depends on the situation. That said, (or can be used in most situations. All you need to do is regulate how short and loud you say it, depending on severity.
When you say loud and short, it unmistakably signals you are scolding the other person. It can be used as a joke, but if you say it to young children they will almost always interpret it as being scolded. It can be used for any severity IMO, and you can basically escalate on a continuous scale. Though if the situation is urgent one might want to shout instructions instead ( etc)