Why was it needed? Narratively it didn't make any sense to me. Aiden had killed everyone involved with the death of his niece, plus all others who opposed him, and a lot of nameless milicia. So why save the guy at the end?

Aiden along the way between wanting revenge and executing his plans did become a vigilante, still his actions never steered away from killing. It doesn't make any sense. Is there any theory that makes saving him a sound narrative choice?

Because it's the "heroic" thing to do, and Aiden seems to be a fucking insane person trying to be Batman.

However I doubt anybody who was involved in the writing of this game intended for him to come off as batshit crazy.

I completely agree. You should read Patrick's article on the subject.

http://www.giantbomb.com/articles/i-dont-think-you-deserve-redemption-aiden-pearce/1100-4960/

I found Aiden Pearce to be one of the most unlikable protagonists I've ever played as, and not in a good way like the characters from GTA V. They tried to pass him off as a hero, a vigilante standing up for the people, but any good he did was incidental. He's a scumbag and the only thing that made him any "better" than the game's villains was that the innocent people he killed simply because they were in his way happened to be presented by the game as pieces of shit in their own unrelated ways.

Yeah, I read it now and I completely agree. The game feels pretty contradictory about the story. He kills a lot of random innocent people, doesn't give a thought to them, appart from the woman in the club, provokes traffic accidents, blackouts, bursts pipes, and is called a vigilante by the public left standing.

He killed everyone that crossed him, appart from the hacker woman, that ended up dying anyway, and would deserve an ending other than killing Maurice?

Well, its narrative is a mess like I've never seen before.

Don't forget flat out stealing from everyone he walks by. Our hero everyone! Stealing your last few bucks from your bank account!!!

Yeah! What a stand up guy!

The choice at the end is a clever judge of character for the person controlling the game. Will you act like a horrible human being and blame it on the video game character or will you do the right thing?

Because they didnt want to leave people with a plot hole to pick at.

It was weird being given a choice to kill Maurice especially when he was the guy who pulled the trigger to kill his niece. I wasn't really in two minds about it at all. I casually walked away then just as I got to the door I turned around and shot him in the head.

Makes me think that most people didn't bother with all the Maurice collectables.