The Who Is Diotrephes Bible scriptures located in 3 John 1:9-10 explains directly from God's Word the Who Is Diotrephes topic.
3 John 1:9
I wrote unto the church: but Diotrephes, who loveth to have the preeminence among them, receiveth us not.
3 John 1:10
Wherefore, if I come, I will remember his deeds which he doeth, prating against us with malicious words: and not content therewith, neither doth he himself receive the brethren, and forbiddeth them that would, and casteth them out of the church.