'I guess this was it.'
Caleb thought as he brought down his Odachi towards the nape of the Apokalip. He didn't mindlessly decide to attack it. It was the result of his careful observation. He noticed that the damn bastard was always avoiding its nape from being exposed to the members.
Not to mention, it didn't escape Caleb's eyes as it tried to cover this part when Jin was about to attack it with his finger gun! What does it mean? It won't do such a thing without a reason. It was its weakness! The vulnerable part! After all, everyone or everything has its weaknesses. No one is perfect, and that's a rule. Of course, there's always an exception, but that's not the case for the Apokalip in front of him.