and gaara chose to kill those innocents, he killed them because they made him feel alive. i dont see your point.
Why did he wanted to feel alive? Because his whole village treated like he wasn't a person but a monster his whole life. He gave into his hatred by feeling alone, hated, and a monster. Gaara's mind was also being tempted by the 1 tails, this happens because the Bijuu can infuse their will in their host with their chakra. We seen this with Naruto many times. Gaara's seal isn't like Naruto's seal, Bee was even impressed with Naruto's seals. Gaara would talk to the bijuu thinking it's his mom, saying his mom wants more blood or at least he did in the anime. Gaara grew up with the Bijuu so if he gave into his hatred and also had the hatred from the Bijuu then his case is not as bad as Sasuke's who wasn't treated wrong his whole life yet instead of only taking his vengeance on Itachi, he took it out on others who had nothing to do with it.
What did Bee do to Itachi or the Uchihas? What did A do to the Uchihas? What did the neutral Samurais do to the Uchihas? What did Karin do to the Uchihas? What did Sakura do to the Uchihas? What did people who had no idea what really happen to the Uchiha in Konoha do to the Uchihas? Nothing but that didn't stop Sasuke from attacking or trying to kill them did it? Can you show me 1 person who was not attacking or in combat with Gaara that Gaara killed when he was evil? You can't can you? He proves his existence by killing the assassins or anyone that threatens him.
sasuke was tortured by his brother who murdered his clan, that same brother tortured him again and told him he is weak, he messed with his insanity. but i forgot to haters, sasuke life was a bed of roses pff.
Gaara was hated and seen as a monster his whole life and had the 1 tails influencing him, was told that his mother hated him and no one loves him, and his father sent many people trying to kill him in his childhood. Sasuke being shown his parents being killed would build hatred towards Itachi who done it (until he found out the truth) while Gaara's hatred was built towards everyone since he was seen as a monster and hated by everyone while his dad is trying to kill him.
It's not about making excuses for either, it's about looking at both of their past, how they were treated in that past, what influenced them, the level of trouble they caused and if they try to make amends. Unlike Gaara, Sasuke known love, he was loved before and after his Clan was destroyed. Sasuke could have stayed in Konoha and go on to be an Anbu who gets missions to track missing ninjas and get Itachi that way but he gave into his Hatred and that hatred kept on going. Sasuke even said killing Danzo gave him a high, that's something evil Gaara would have said as well but that's Gaara also being influenced by a Bijuu who has a deep hatred fro humans for how they treat Bijuus, all Bijuus felt this way until they met someone who was kind to them and saw them more than just weapons.
Gaara's hatred did result in many deaths but the majority of them were people trying to kill him or attacked him (in a fight that goes with fighting him). Gaara did try to kill Lee when they fought but he didn't thanks to Gai and after that Gaara was saving Lee from Kimimaru many times in that fight so he was making amends by saving him. Sasuke's hatred directly and indirectly caused many deaths, those who died from the Juubi, Juubito, and Juubidara are all Sasuke's kills indirectly since he was the one who helped made it possible for the Juubi to be revived by giving Obito a portion of the 8 tails chakra while thinking it was the full Jinchuuriki.
Lol @ some of these answers justifying Gaara
How so? None of the Jinchuuriki ever witnessed anything traumatic like that and had to relive it a bunch of times caused by the person closest to him, oh wait and then when he gets his "revenge" on that person he finds out he was doing all of that to protect him and he was happy about it, and not to mention his clan history of the Butthurt Uchiha Syndrome made him delve into the darkness deeper than Gaara but my point is he is one of the deepest written characters in Naruto. Jinchuurikis had no friends? BOOHO... Its a little worse than that in Gaara's case as he had been lied to as well and had a lot of issues in his family and he is also one of the most justified psychos in Naruto (when he was evil and he was just as badass if not more as sasuke was when he was evil at that point).
Never witness anything traumatic? Being looked at with hatred in all the eyes of the villagers, being called a monstered, being told you're the reason for your mom's death, being told no one loves you, having people trying to kill you and sent from your father all when you're just a little kid is not traumatic? All Jinchuurikis went through something like this, the only similar thing would be that that they are seen with hatred and as monsters but the details would vary. Gaara thought the 1 tails talking to him was his mother....how messed up do you have to be for that? Your mom telling you she needs blood so to kill those that are attacking him.
Sasuke's hatred is justified but how he went about it isn't, he didn't have to take that road since he knew about bonds and about being loved before and after his clan died. The villagers all saw Sasuke as a elite and Sasuke had people who wanted him in their lives but he cut those bonds and go into the darkness to get Itachi. Sasuke could have stayed in Konoha to achieve the same goal, is being trained by Gai, Kurenai, Kakashi, and Asuma not good enough for him? Itachi himself told Kisame not to take Gai lightly and Gai have knowledge on fighting Uchihas while improving his taijutsu and speed. Kurenia helps him with Genjutsu, she was said to be a high level genjutsu user as Itachi, could have trained Sasuke. Sasuke even joined Obito when he knew Obito helped Itachi kill the Uchihas.