Sasuke obviously- Sasuke is actually very impressive and entertaining to watch, his complex life story and the tough choices he makes along with the difficult challenges he faces makes him the arguably the most relatable character in Naruto. His design is great and he always brings something new to the table, he's cool, calm, and calculating, able to quickly analyze the situation and respond accordingly. Dispute sasuke being a prodigy he's always felt ostracized from people, he's the easiest character to emphasize with that dispute being mentally scarred by his brother, branded a criminal, and just confusing overall, he still manages to get most things done and endure. Though Naruto does the same, Naruto is more of the typical "everyone hates me, so I shall work hard and now everyone loves me" people have seen this over and over, sasuke is an anti-hero and people love anti-heroes because their complex and enjoyable to observe. Batman, deadpool, incredible hulk (arguably) to name a few. And to see such a person whose been through hell and back still in the end, ever since chapter 699 be a hero is something truly inspiring creating the reoccurring theme that even those knee deep in darkness can be saved.