Gamabunta rapes Sasuke. Naruto didn't summon him. And its true people are saying Naruto can't summon Bunta without kyubi chakra but that's only because he didn't have good chakra control again because of kyubi. Something which he improved with training by part 2. So even without kyubi he should be able to summon Gamabunta.When Naruto was knocked out cold in the rain, Sasuke could have stabbed him to death, or suffocated him.
Just because Naruto refused to fight seriously doesn't mean hes "holding back". He fought his hardest and still lost, and even got aid from the Nine-Tails and still he lost.
Pretty pathetic.
And talking of aid from the Nine tails then Sasuke too had curse mark. But ofc you'd forget that.