Final answer:
The individual expected to explain all things when he comes, according to Christian theology and closely related to John Chapter 14, verse 26, is the Holy Spirit, who is sent to teach and guide believers.
Step-by-step explanation:
The passage referred to seems to have a typographical error, as there is no John 25. However, in similarity to the concept of the one who will explain all things, John 14:26 in the Bible mentions "But the Comforter, which is the Holy Ghost, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you."
This implies that the Holy Spirit is the entity that will explain all things when He comes.
The verses provided (MT 3:12, 8:12, etc.) refer to different Biblical concepts including judgment and the consequences of sin, but do not directly speak to who will explain all things. Nevertheless, it is commonly understood within Christian theology that the Holy Spirit acts as a guide and teacher for believers, providing understanding and wisdom according to the teachings of Jesus Christ.