User blog comment:Xilinoc/Ch. 609 - "A"/@comment-25606271-20141211185605/@comment-24963493-20141212012708

Yamamoto was the strongest of the 13 Court Guard Squads. Ichibei is (assumed to be) the strongest of the Royal Guard, the five of whom are more powerful together than all the 13 Squads combined. So, yeah, Ichibei is stronger than Yamamoto, and he definitely stood more of a chance against Yhwach than Yama did.