Yet, having said that, when a person throws acid in another person's face that is a pretty brutal and irreversible act. I have no problem with that person being dealt with in a brutal, irreversible way, and no it doesn't make the state "just as bad". Their action was provoked and his was not. The victim herself says that she hopes this man's punishment will deter this all too common type of activity on the part of men. Perhaps revenge isn't the most noble of sentiments. Instead of focusing on harming the other person, it might be better to focus on fixing the injury that did occur. However, when one has been gravely injured and one's rights have been violated the victimizer has created the justification for defensive retaliation, even if that retaliation is in cold blood.
Now some people seem to think that self-defense only applies at the moment where one is fending off an attack. However, defense is not exclusively confined to the moment of an attack. Defending one's country, for example, is something that can be done even outside the heat of the moment. If one is injured in battle, then one can still be defending oneself from enemy aggression by attacking them in another battle, on another day.
It's absolutist thinking to believe that something, like injuring another person, is always wrong, no matter what the circumstances are. If someone punches me in the face with no justification then they have created the circumstances, by their unjustified attack that very definitely justifies me punching that person back. If, one day, I am too old and weak and arthritic to smash that person's back in the face then I expect the state to defend my rights for me.