Could a Chuunin really take on like 1000 Narutos? Well, I dunno, it would seem like a stalemate to me. The skills and experience of a Chuunin are still unknown since we have only been affiliated with Genins and Jounins, although it's probable that a Chuunin would be smack in the middle. Still, taking on 1000 Narutos would be tough. The only thing I can think of is that all the shadow replications all attacked at once, giving Mizuki little chance to dispel the replications.