It is obvious
1. He is the second main character
2. He is equal to Naruto, maybe not in power, but they both can't exist without each other and are rivals
Look at some popular anime:
DBZ-Vegeta as bad, became good
YUGIOH-Seto Kaiba was bad, became good
INUYASHA- Sessomaru was bad at first, helped Inuyasha in the end
AVATAR- Zuko became good later, even if he was bad at first because of his dad
1. He is the second main character
2. He is equal to Naruto, maybe not in power, but they both can't exist without each other and are rivals
Look at some popular anime:
DBZ-Vegeta as bad, became good
YUGIOH-Seto Kaiba was bad, became good
INUYASHA- Sessomaru was bad at first, helped Inuyasha in the end
AVATAR- Zuko became good later, even if he was bad at first because of his dad