I have mentioned three ways I can imagine the character going. I have included descriptions and links to the source of the names, so you get where I'm coming from.
Lawful Good: There is a better way. The killing is a cycle, and the only way to stop it is to stop killing. Well, mostly. Some idiots are always trying to ice-skate uphill.
The body politic is ill. The bureaucracy is bloated; the fat must be cut away. The muscles of the military flail uselessly; they must be stilled. The skeleton of society, the worker classes, are crushed beneath the weight of it all; their burden must be relieved. And the cause? The head is poisoned; it needs some decisive surgery.
They--not the Resistance, but your brothers and sisters, fathers and mothers, the family you had forsaken--have a word, and that is coup. Bloodless or not, supplanting the government and replacing its most vital members could achieve in one fell swoop what all the bombs in the world could not. The machine isn't broken, after all; it's just being put to poor use...
And who better to run the machine than the finest men and women humanity has to offer?
True Neutral: All that matters is the fight, and vengeance. Ripping the WEC down, soldier by civilian by building, until nothing is left but ashes and converts. Let the Resistance worry about the bigger picture, guide you like a ballistic missile. You're more than happy to do their dirty work. It's what you're built for. And when it's over, they'll cast about to give you a medal for your bravery...but it's not bravery, and they used the services of a man they didn't understand. With the task done and your fellows avenged, you are nothing, and you'll just fade away...
Chaotic Evil: When you get right down to it, the Resistance doesn't seem to be that effective. They would have been crushed if not for the Silencer. What's needed, then, is a better class of terrorist. One who's very good at getting bombs in and would not be restricted by conscience in choice of targets. The operative word is
terror. It's not even about the cause, so much as it is about the message being sent: you are not safe.
Of course, such haphazard, reckless, seemingly purposeless wholesale destruction would cause the Resistance to try to rein him in. And they would fail. Oh, how they would fail.
Now the Silencer is without support, but that's fine, because that means he gets to improvise, which is where he and his kind get dangerous. Who would expect a small tactical nuke in a neighbourhood with no tactical significance whatsoever? From the lore standpoint, this branch of gameplay would result in the most deaths, but the player would be stealthing most of the time to get bombs into play, rather than killing them in straight combat. With minimal resources, he would be forced to conserve them, and make every hit count.
And he would.