can a villain win if the hero has killing intent?
Hashirama held back against Madara
Hiruzen held back against Oro
Jaraiya held back against Itachi
Naruto held back against Sasuke
Guy held back against Itachi
Itachi held back against Sasuke
With hero killing intent and bloodlust, Naruto would've ended 95% of all shinobi himself
If anything Naruto was the villian. He was trying to forcefully subdue and bring someone back to a place they didn't want to be. Whereas Sasuke was the hero who tried getting justice for the Uchiha whilst the village was proven to be incompetent.
A younger Itachi murders the village's strongest clan - the Police Force. Then he returns older and stronger, infiltrating the village declaring that he's after it's Jinchuriki - Naruto. He whips two of their top Jounin with his fellow S-Class internationally wanted criminal partner - Kisame of the 7 mist swordsmen, being with him whipping another. Gai arrives saying he called backup then they run away. They managed to find Naruto who was unexpectedly with Jiraiya - a Sanin, and manage to escape again. Does Konoha continue to pursue them? No. That's as far as they go. Logically they should have done their best to apprehend these criminals.
Meanwhile when they hear about Hidan and Kakuzu, two less powerful enemies, they send out their troops to handle them til they're dead. Big difference right? Maybe Konoha knew they didn't have anyone strong enough to deal with them so they didn't bother to expend their manpower? Nope, we find out that the higher ups are in cohoots with Itachi, having ordered him to carry out genocide and leave the village as a rogue shinobi.
And calling Itachi a hero against Sasuke is even more ridiculous. He went behind the Hokages back, listening to an oppressive dictator's orders to wipe out a group of people who were being persecuted and just wanted civil rights. People who were purposefully pushed to the point of rebellion so he could use that as an excuse to execute them in the name of "maintaining peace". Which ironically put the village in great danger as they had lost their strongest clan within a single night. Other villages could have use this as an advantage and attacked the now weakened Konoha.
As for unnerfed battles, Kishimoto restricted Sasuke from utilizing his copying ability to his full advantage throughout the entire series so he wouldn't become too strong to quickly.
Kakashi - a non-Uchiha who is negatively effected from using the Sharingan, managed to copy over 1000 techniques. Sasuke could do alot better.
Through his intelligence & training he was already able to make extraordinary progress in rapid succession within a short amount of time. Hence learning both his nature elements in days well enough to master high level jutsu in addition to gaining Lee's level of High Speed Taijutsu without the weights, despite it usually taking Shinobi years just to hone their element alone.
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Now factor in being able to perfectly copy techniques just from seeing it once.
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Furthermore, Sasuke was stated to be greater than Itachi & Naruto.
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