One word: "Absolve." At the front desk of the police station. And this is for a sidequest. (Although pulling this off also makes a main quest many times easier.)
Though you shouldn't lean too heavily on it; depending on how he reacts and his mood, this could actually piss him off because you're being sanctimonius.. But yeah, a successful end to that dialogue is very heartwarming.
His responses are actually random. Reload that conversation and you'll get completely different responses. Which actually makes some sense, considering how much stress he's under and the fact that he's on anti-psychotics. No wonder he on a hair-trigger.
On the whole, if you choose Plead and/or Absolve for the majority of the conversation and choose Crush at the end, telling Haas point-blank that he chose to pull that trigger, no one else, and that he needs to take responsibility for that and put it behind him, you can convince him to turn his life around. Probably because it's the truth, and he knows it: Adam refused to pull that trigger. Haas could have, too. But he didn't. Especially on-point if you manage to hit the dialogue where Wayne tells Adam that he blames Adam for everything that happened, including the fact that Wayne shot the kid. Regardless, hearing him come to the realization that he has to turn his life around is a CMOH as well.
Wayne: Aw, hell... You're right. I've been so stupid! Two whole years... I've gotta start turning things around. Right now.
The monument to those that died in the attack in the opening scenes of the game. It's little touches like these that get people interested in a game's world, after all.
Returning Megan's bracelet to her grieving mother.
On a side mission in Detroit during the riots, you find out that you are adopted and that your real parents died in a fire they caused to save you from being used to inoculate other babies in a gene therapy research facility. You find this out from a senile woman who took you from the facility before the fire started. You then have a security detail come to her home to make sure that she is safe,because you consider her family. For this troper, this was especially moving.
That and she gives you, er, Adam Christmas and birthday money for all the ones she missed. I genuinely felt bad that I took her money right after.
Why? You tell her you'll get the money to Adam and she wanted to give it. As far as she knows the money will get to Adam Jensen and in reality she just handed the money to Adam Jensen, it's a win win.
Because logic doesn't always coincide with heartwarming.
Jensen's apartment has a table covered in get well soon cards among the bottles and bottles of medicines. It really connects him to the setting and makes it clear that people do care about him.
If you talk to a hobo, one of their random responses is to say "Thanks for talking to me. Most people just walk on by like I'm invisible." Considering most gamers would just ignore every NPC as they went on their way, hearing that is the kind of thing that encourages one to spare the person who said it from their knockout spree.
Malik and her special mission and saving her from death after the plane crash result in heartwarming moments.
"Any time, fly girl."
Frank's reaction upon first hearing from Adam after a few days of Adam being MIA, along with his genuine concern over Adam being effectively on his own on Panchaea, without Frank as his Mission Control. It's such a huge change from his initial disdain.
Talk to the Sarif employees, including the security and janitorial staff. It's obvious that Adam is well-liked; anyone who talks to him about himself either wishes him well, is glad to have him back, feels safer having him around, expresses concern over what he's been through, tells him not to push himself too hard, or some combination of the above.
The point where I decided, "Let's do it, Sarif!" was meeting him at Panchea. He'd been schmoozing me since minute one, hiring me solely because Megan wanted my DNA For Science!, Rebuilding me from the ground up when all I really needed was a new arm, stomach and head, keeping my Mysterious Past as one of Bob Page's guinea pigs from me, all in all convincing me that he was just the best alternative to the sick, twisted monsters I was fighting. But his first words upon seeing me in Panchea sold me - this guy's manipulative and elitist, but he genuinely wants to help the human race overcome its weaknesses through augmentation.
A strange mix of heartwarming and a tearjerker is Pritchard's response to Malik's death, as it really hammers home just how much he haswarmed up to Adam. One person he cared about was just killed; he doesn't want to lose Adam, too.
Adam: Bastards ambushed us, Pritchard! Malik didn't make it! Frank: Oh. God... I--I know you... might... want to get even. But if they see you; if they recognize you--! It might be better to stay out of their way.
Adams's speech after destroying Panchea (with a pacifist run), explaining that, while he doesn't really know whether or not humanity can save itself, he believes that basic human decency will hold out, and that it's not up to anyone else but them to build the future; not Sarif, not Darrow, not Taggart , not even himself.
Adam: Do I trust humanity to save itself? That's what Eliza was asking. The truth is, I don't know. After everything I've seen, all the fighting, and the chaos around me, I only know what I want to believe: somehow, Human decency will triumph. These past few months, I've faced many life-threatening situations. I could have given up many times, but my need to know the truth, to uncover the secrets that others were hiding, and to survive forced me to keep on going. Most of the time, I tried to keep my values in mind, knowing my actions did not have to harm others. I held on to my humanity, resisting the urge to abuse power or resources in order to meet my goals. And in the end, I got the job done. But does this mean I have the right to choose for everyone? No. Because it isn't up to me. It isn't up to Darrow, Sarif, or Taggart either. Ordinary men and women will have to decide together what course mankind should take. The kind of people who, time and time again, have picked and chosen the future in highly practical ways -slowing change when it's negative, spedding it up when it's good. Can we do it again? I don't know. But I do know that I'm not about to let anyone in this station , myself included, stand in their way.
Michael Zelazny, in a world of cruel self-serving mercenaries, Zelazny and his men are the only ones who joined for the purpose of defending people which the reason they go rogue from Belltower after finding out that their operations were for corrupt politicians. More here.