At what point in his storyline could Naruto successfully stop the rumbling? (Attack on Titan)

I'm quite sure he could with his current strength level, but what do you think was the earliest version of him that could do it.

Round 2: same question for Sasuke

Round 3: Naruto and Sasuke work together

Edit:

Round 4: killing Eren won't stop the rumbling, he has to literally kill all of the 100,000's of titans