If there was a time bomb on the ground floor of an apartment building, would defusing that bomb be a form of violence?

It doesnt sound like violence, just because it's not your property. Try trespass or a property crime.

I don't think so. In extreme circumstances where you can save lives, the laws of trespass and destruction do not apply. As long as you're convinced it will save lives, I think. (but not entirely sure).
But if you don't know how to defuse a bomb, then proceed to deface and destroy the building, then probably have the bomb go off anyway - it could be a form of ..well, stupidity, if not manslaughter.

#BeingLibertarian

Violence is like obscenity. You know it when you see it.

If doing something to save countless lives is violence. Great. Let’s do violence.

Is it morally OK to tread on a snake. Say - a yellow snake if it's on your property?.

all existence is violence