There has been no greater fictional contrast of brothers morally than that of the Uchihas.

I'll just use a table to reiterate my points and outdo you in number of fundamental differences/clashes. I'll also be relying on reader's having read round one as I'll refer to Itachi's killing of Uchiha clan a lot as well as understanding of why he let Sasuke kill him (to spread the sharingan eyes). If you disbelieve the validity of the quotes I use (since some are from the anime-only and not found on Google) ask anyone who has seen all Naruto episodes or Google them (most are famous and are found on fan sites). Although both are atheist, they are so to a different extent, Itachi being the more rational and passive one. Belief in God Agnostic Atheist Famous quote from a fight with Sasuke (this is so famous that it is attributed to him in all quotes so you can even google it): “People live their lives bound by what they accept as correct and true. That's how they define "reality". But what does it mean to be "correct" or "true"? Merely vague concepts… their "reality" may all be a mirage. Can we consider them to simply be living in their own world, shaped by their beliefs?” Gnostic Atheist When Naruto and Sakura try to save him at beginning of Shippuden: “I have no ‘master’. Orochimaru is not holding me against my will. I am merely here to train and then to execute my revenge on Itachi” Sasuke hates the word “Master” or “God” and when he takes over Orochimaru’s clan, after killing him, he never requests them to call him master Sasuke. He is extremely arrogant of the ‘fact’ that there is no supposed hierarchy or supreme being of any kind whatsoever shown through both actions and the fact that almost all enemies of his are strong believers in God (aside from Itachi who he hates for personal reasons). Existential View Nihilist Same quote “People live their lives bound by what they accept as correct and true. That's how they define "reality". But what does it mean to be "correct" or "true"? Merely vague concepts… their "reality" may all be a mirage. Can we consider them to simply be living in their own world, shaped by their beliefs?” Existentialist/Subjectivist After killing Itachi and learning his brother’s true predicament in killing the Uchiha clan, Sasuke somewhat forgave him and then he decided that spreading hate around would best serve his brother’s original cause. All his morals and actions are rooted in the subjective experience of emotion (as existentialists believe). "If you think I'm just a foolish kid ruled by his emotions, that's fine. Following Itachi's path would have been too childish, the whispering of fools who don't know hatred. If anyone else tries to ridicule the way I live, I'll slaughter everyone they ever cared about. And then maybe they'll understand what it's like to taste... a little of my hatred." "Just shut up for once! What the hell do you know about it?! It's not like you ever had a family in the first place! You were on your own right from the beginning, what makes you think you know anything about it?! Huh?! I'm suffering now because I had those ties, how on earth could you possibly understand, what it feels like to lose all that?!" Moral Views Utilitarian The choice to kill his entire loved family for the sake of saving more people than he would kill shows this. Nihilist Has no apparent moral code whatsoever and every act he ever did was merely on a personal whim. First quote is when reasoning about using Itachi’s eyes (which were granted to him upon his killing of him) even though he’d spent his whole life trying a way to gain power without gaining Mangekyou Sharingan. "I understand now. Even if I must take the devil's fruit, I must gain power. I am an avenger." He even doesn’t kill Naruto and then later tell him that “"I spared your life on a whim, nothing more. But this time, my whim is telling me, to finish what I started..." Relation to Pain Masochist Not only does he go on with the emotional burden of letting his brother live thinking of him as a viallain, as well as all others WILLINGLY but also keeps himself alive for about three years while extremely sick, on a medication, so that he can be alive for the day his brother kills him (as only if he is killed by his brother can he pass the Sharingan he’s obtained onto the killer). Sadist His actions are that of a merciless brute who gains pleasure form other’s pain. He also has quotes after killing Itachi. When speaking to ‘himself’ before trying to tear Konoha (leaf village) apart: "They're all laughing. you're laughing at the cost of Itachi's life laughing together completely ignorant of everything. your laughing voices sound like contempt and mocking me now, I will change those laughs to screams and wails" When speaking to himself thinking he’s speaking to Itachi’s spirit and going against everything his brother wanted despite his new-found love for him (after realising the truth of his killing of the Uchiha clan which I explained in round one). “I guess anything I say now would be pointless… When I saw you… I decided to follow you here to confirm whether or not what Danzō and Tobi told me was true or not. But that wasn't the only reason… When I'm with you I remember the way it used to be. I remember time spent with the brother that I looked up to… that I loved. That's why… The closer I get to you… The more I'm able to recall what those days felt like… And the more I'm able to understand you.The more I'm able to hate Konoha for the suffering they put you through. In fact, it's becoming even stronger than before. I do understand what you want me to do. It's probably because you're my older brother that you feel the need to put me on the right path. But it's probably because I'm your younger brother that I'll never stop, no matter what you say. As you'll always exist to protect the village… so will I to destroy it. Goodbye… brother.” Dmitry=Itachi and Sasuke=Ivan in terms of humility Itachi was a humble servant to the village’s leader of ANBU black-ops and hence followed the order to wipe out his family. He always kept the secret to his grave and always spoke in a very humble, kind manner even to his enemies in the heat of battle. He was by far the most polite member of Akatsuki (although he was only a member of it as a spy for Konoha). Sasuke was always arrogant, probably fuelled by his hatred and envy of Itachi as a child since their father always compared them and rated Itachi as his favourite. He has this quote from when he had to explain why he wanted to be a ninja, he said it in front of his Sensei (teacher) as well as Naruto and Sakura. “My name is Sasuke Uchiha. I hate a lot of things, and I don't particularly like anything. What I have is not a dream, because I will make it a reality. I'm going to restore my clan, and kill a certain someone.”