Relation between violence and revolution in "A Tale of Two Cities"

Maybe the most meaningful quote dealing with the relation between violence and revolution is: "Good could never come of such evil, a happier end was not in nature to so unhappy beginning". I infer from this quote that Dickens wanted to say that if you want to change something positively, you have to be aware how do you to it. A major motive in this book is vengeance. Vengeance is not rational and serves to satisfy one's bad tribe but not the goal "revolution" or a better society. But the question which arouses right now is: Is violence in general the wrong way to achieve a better world? I would go so far and say not but, a big but, violence is not supposed to serve as a valve of aggression or sadism. It must be always reasonable and of course the last choice of every possibility.

The good intentions are poisoned by the wish for vengeance:
"Nothing that we do, is done in vain. I believe, with all my soul, that we shall see th triumph. But even if no, even if I knew certainly not, show me the neck of an aristocrat and tyrant, and still I would-"

"It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness, it was the epoch of belief, it was the epoch of incredulity, it was the season of light, it was the season of darkness, we had everything before us, we had nothing before us" - these are the first word from this novel. It shows in wonderful way the ambivalence of this revolution.