How?

Once Ractopictan changed his form it was like fighting an entirely different opponent. The rhythm of Ractopictan's attacks was completely different from before and it took some time for Erste to get used to it, which almost got him into trouble. 

This was the first time since defeating the New God that he first fought that Erste felt his life was in danger. Even when he fought the powerful Old God Agares he had not felt such danger. This feeling of being in a life-and-death situation had made Erste both afraid and excited at the same time.

Despite the opponent being of similar size to himself, Erste found it surprisingly difficult to fight more so than normal. He had been so used to fighting opponents that were the size of planets and most of his new techniques were meant for such opponents, which is why it took him some time to get back into proper fighting form. After a while, Erste's attacks were becoming sharper as he started having fewer excess movements.