For myself on this question, and most others like it, I simplify the reasoning process by asking two questions.
What was the actual intention of the Good Man, as best as can be determined by 'me'?
Could his 'action' to fulfill his intention be considered appropriate under the circumstances (especially to him, given what he could reasonably have known at the time), or was it arbitrarily and/or negligently and/or irresponsibly determined and excecuted?
If is intention was correct, honorable and 'right' by the judging standards, but he irresponsibly did not look at all possible options or take proper precautions, or otherwise manage his actions then, given a disasterous outcome, he could be considered just as evil as the Bad Man. i.e. a loose cannon.
But if judged his intention was correct and proper (to stop the bad man) under the circumstances, and also judged that he made every reasonable (subjective yes, but something the judging party must decide) effort to find the 'best' solution before acting, and executed that action to the best of his ability, then he cannot be considered equal to the Bad Man at all.
And like everything else in the universe except gravity, this is not an absolute process. But it is the best one going for me.