>>46382155It was someone who'd gone Ohma prematurely and barely understood his own powers. Decade pulled out a new EVEN FURTHER BEYOND form called Complete 21, only for Ohma to shrug off his finisher and KO him in a single blow. Then Zi-O used a lazily-designed Saber form (which should be weaker than even Decade's base form) and killed Ohma.
In context, the Saber armor wasn't actually depicted as stronger than Decade - rather it was Ohma committing assisted suicide. Because while Decade is overpowered, Ohma has always been depicted as truly omnipotent, to the point where the only feasible way of stopping him is by travelling back in time to stop him being born.