Sasuke is one of the most popular characters of all-time, not just Naruto. However, he has also left behind a good number of funny anecdotes memes and whatnot. One of the most amusing topics about him, is that despite being depicted as a villain for a long time, his kill count is actually much lower than characters described as benevolent. This might seem as ridiculous at first, but when you start looking back at certain moments, the whole picture changes.
Time and time again, Masashi Kisimoto made sure Sasuke wasn't crossing the line to become a murderer. In fact, even before he left the village he was a recurrent Batman type. A great example of this phenomenon were the Sound Village ninjas during the Chunin Exam.
Under Orochimaru's Guidance
His life was always surrounded by death. Part of a clan famous for killing each other to gain power. As a child, witnessing how his brother murdered his entire clan. Hard to talk about mental health from that point on. He got consumed by revenge and hatred. Sasuke's only purpose in life was to kill his brother Itachi and restore the Uchiha clan. This led him to abandon and betray his friends seeking for the power needed to accomplish his task.
Right at there at the end of Naruto he had the first chance. After an epic fight with Naruto, he was the last one standing. He had the chance to finish him off which will also grant him more power, as Itachi told him, killing his best friend would awake the Mangekyou Sharingan. He decided not to, the first of many moments where Sasuke didn't cross the line during his evil phase.
Even after the time skip some of his old-self was still there. Orochimaru would bring him hundreds of fighters to train and purposely knocked every single one of them out without killing them, which actually shocked Orochimaru. He was only going to kill Itachi. When Naruto and Sakura found him, he proceeded to miss another chance to kill any of them. When he finally reached enough strength that made Orochimaru useless, he attacked him in what seemed like the first murder, or so everyone thought. Truth is, Orochimaru was still living inside his curse seals recipients.
Revenge Saga
Now on his own he formed the ultimate team to kill Itachi and started seeking for him. On his way, he bumped into two other Akatsuki members, Deidara and Tobi. Deidara also had a personal grudge against Itachi and couldn't let Sasuke get him first, leading to one of the most exciting fights of the entire series. Deidara vs Sasuke had some great moments and concluded with Dedidara's death. Yet again, it was not by Sasuke's hand. He committed suicide in a desperate attempt to defeat him in a spectacular way which should be considered art.
Time went by, and he finally met with Itachi for the final fight he had been searching for so long. An even more epic fight, but as it was revealed later, perfectly orchestrated by Itachi. He was in the latest stages of a sickness caused by the overuse of the Mangekyou Sharingan but wanted to settle things with Sasuke before dying. His mission was to kill the Orochimaru inside his younger brother, help him perhaps unlocking Mangekyou and facing his crimes dying by his hand. However, the real cause of death was exhaustion. He collapsed in front of Sasuke when both of them were out of stamina to continue. Another missed opportunity.
Akatsuki Membership
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This is the moment when he actually turns completely evil. Torn apart after learning about Itachi's truth he decided to join the organization he was spying under the orders of Danzo. His first mission was to collect the Hachibi alive. It suited him well, and he almost managed to do it but went back with just a tentacle. Although his aggression showed to be on another level now.
Now the series faces a key moment. During the 5 Kage reunion, Sasuke, for the first time, went on an actual killing spree. He killed an undetermined number of Samurai soldiers. Maybe Kishimoto deemed that those secondary characters didn't really matter, plus it gives a better perspective on his mental state at the time. But after so long, he actually killed someone. He then fought against the Raikage and his subordinates but without fatally injuring anyone else.
Exploiting the momentum, he attacked his real target coming back from the meeting, Danzo. The now Hokage was responsible for most of Itachi's suffering. Another great battle for Sasuke that ended in the opponent committing suicide, although to be fair he did almost kill Karin and Danzo. Right after, Sakura arrives at the scene in a weird attempt to kill him. Sasuke almost kills her, saved by Kakashi and Naruto at the right time.
Fourth Great Ninja War
During this time he goes back to being a gray character, and it's all thanks to Itachi. He comes back thanks to the Edo Tensei. Sasuke had just implanted Itachi's eyes to get the Eternal Mangekyou Sharingan and eh knew right away he was there somewhere. They encountered after Itachi freed himself from the Edo Tensei and went onto stop Kabuto. They fought him together until Itachi got him under the Izanami jutsu. After a very small talk, Sasuke was even more dear to his brother, and wanted to rethink his life.
A talk with the 4 past Hokage, brought back thanks to Orochimaru's Edo Tensei, got him thinking that he wanted to become Hokage and change the world for better. Sasuke joined the battlefield where almost no one died. He and Naruto were on the blink a couple of times, but instead they gained more power to face Madara. Unless killing Zetsu clones counts, he didn't kill anyone during the war.
Ultimate Clash
The reunion of Team 7 to save the world didn't last after they finally sealed Kaguya. Sasuke tried to murder Sakura once again and failed. Trapped all the Bijuu and challenged Naruto to a decisive fight. Before starting fans already knew both were going to survive, because they needed the power of the other to release Mugen Tsukuyomi. Still, they went all-out in a spectacular fight. At the end, they lost their dominant hand, had a little friendship moment and everyone was happy.
Naruto Shippuden was supposed to portray Sasuke as the main antagonist, but failed to give him enough evil acts. Sasuke's kill count by the end of the series was a bunch of Samurai most people don't even remember and that didn't change the story in any form. But again, if Kishimoto's plan was to avoid making the protagonists look like murderers, it was successful. He might not be your ruthless villain, but he was an amazing and relatable antagonist regardless.