If you're looking at the Kyuubi that Naruto had fighting against Obito and his Six Paths, remember it's only half the Kyuubi's power.
Also, IIRC Naruto and Minato fused their chakra with each other in which they technically had 100% of Kurama's chakra - and now add sen chakra which should make Kurama even more powerful.
Edit: And no, I meant the Kurama which fought against Sasuke at the end.