These are my reasons:
1. His speed was unbelievable, was fast enough to the shock of yamato(a member of anbu) and even deidara(an S ranking akatsuki member)
2. He defeated deidara without the intent to kill in order to learn about itachi's whereabouts, someone even kakashi with his kamui had a tough time with.
3. He was capable of summoning the greatest summon of orochimaru(manda) and even control it with genjutsu even after a tough fight.
4. He was capable of fighting itachi(though there was no chance that he would win), itachi acknowledged his power.
5. Just being taught one jutsu (chidori), he manipulated it to form other strong lightning jutsu's, remember the chidori senbon, chidori nagashi and chidori spear are jutsus even kakashi(the creator of the jutsu), is yet to display.
6. He creted a jutsu capable of destroying itachi's v2 susano and their battlefield.
7. Even the kyuubi noted his chakra at that time to be powerful.
8. His ninjutsu, genjutsu and taijutsu was on a different level compared to jounin level shinobi.
9. His intelligence was quite good, as seen when he fought deidara and even after the fight, noted he had another plan incase the other didnt work out.
9. Wiith his summon as manda(if it didnt die), he would have taken any konoha shinobi at that time(exluding Jiraiya and danzo)
This are my reasons, i need reasons if you think otherwise.
1. His speed was unbelievable, was fast enough to the shock of yamato(a member of anbu) and even deidara(an S ranking akatsuki member)
2. He defeated deidara without the intent to kill in order to learn about itachi's whereabouts, someone even kakashi with his kamui had a tough time with.
3. He was capable of summoning the greatest summon of orochimaru(manda) and even control it with genjutsu even after a tough fight.
4. He was capable of fighting itachi(though there was no chance that he would win), itachi acknowledged his power.
5. Just being taught one jutsu (chidori), he manipulated it to form other strong lightning jutsu's, remember the chidori senbon, chidori nagashi and chidori spear are jutsus even kakashi(the creator of the jutsu), is yet to display.
6. He creted a jutsu capable of destroying itachi's v2 susano and their battlefield.
7. Even the kyuubi noted his chakra at that time to be powerful.
8. His ninjutsu, genjutsu and taijutsu was on a different level compared to jounin level shinobi.
9. His intelligence was quite good, as seen when he fought deidara and even after the fight, noted he had another plan incase the other didnt work out.
9. Wiith his summon as manda(if it didnt die), he would have taken any konoha shinobi at that time(exluding Jiraiya and danzo)
This are my reasons, i need reasons if you think otherwise.