The war was glorious.Others found horror. You found a purpose. You existed to kill. It turned out you were extremely good at it. Every time you took out an enemy, some of your men got to live for a while longer. More of those under your command went home than from any other unit in the country. You would have given anything to stay there forever, in battle eternal.
(Sometimes you wonder if you did.)
But you had to come home: that was the rule. And when you did, you -- couldn't adjust. Your skills cried out for use. The country you had returned to had no place for you. Veterans were not honored: just shoved aside into places no one would have to look at them. Your family had become alien. You had no way of relating to them. Criminals approached you, asked if you would become their gunman, and part of you wanted to agree just because it meant holding a gun again -- but you said no.
You had no idea how to be with your children. You were no longer able to speak with your wife. All you could think about was war, endless war.
So you took them to the park. One last beautiful day together as a family.
The last words you ever spoke to your wife -- the final thing she heard before the criminal's bullets killed her right in front of you, your refusal to work for them bringing back consequences -- was your request for a divorce.
Your wife has been dead for decades, as have your children. But they remain with you as motivation. You go out every day and night with the weapons and wage war eternal against criminals. You take no prisoners and leave none alive, not even to tell the tale and warn others. Because someone must be punished.
http://tvtropes.org/pmwiki/pmwiki.php/ComicBook/ThePunisher?from=Main.ThePunisher
And that someone is you.