Zhu Yi never meant to underestimate Lin Daohan.
Before the rise of the Celestial Sect of Wonders, the Great Void Sect was the premier cultivation place in the Divine Lands. Every single disciple of the Great Void Sect had to be exceptional to join the sect.
Anyone who could join the Great Void Sect and become a direct disciple of the sect must be exceptional in their cultivation abilities, at the very least.
Lin Daohan was the most exceptional cultivator of his generation. He dominated the top position in the Great Void Sect and he surpassed all his peers. Indeed, he was the genius of the genii.
While he resided quietly in Mount Baiyun all these years and hence, very few people knew of him, those who did knew the true magnitude of his power.