At the end of the day, Greninja was banned by roughly an 80% majority and made history as the second starter to be banned from OU.

Is Ash Greninja banned?

7 Banned: Ash-Greninja

It may not have Protean, but it has something even more potent in its place: Battle Bond.

Why is Greninja not uber?

This, combined with Protean and its Speed, made Greninja a complete nuisance to offensive playstyles and borderline invalidated balance playstyles. Ultimately, this proved to be too much for the OU tier to handle, and Greninja was eventually banned to Ubers.