Ask a Jehovah’s Witness if there is only one God. They will agree Jehovah is the only God.
Then ask if Jehovah is an Almighty God or a mighty God. They will say he is Almighty.
Have them to read Isa. 44:6-8 “besides me there is no God.” And have them agree with it.
Then have them read Deut 6:4 Jehovah our God is one Jehovah- have them agree that there is only one God who is Jehovah
Ask them if this is Jehovah speaking, Isa. 45:5-6: “I am the LORD, and there is none else, there is no God beside me.”
v. 22 with the exception of me there is no God."
Is this god Jehovah?
They will say certainly not- Jesus is only a mighty god, because they believe Jehovah created him.
Then ask the Jehovah Witness if this mighty God can be Jehovah- they will definitely make the point that there is a difference.
State: if Jesus is called the mighty God, then this does NOT make him God? Correct?
They will agree- only Jehovah is the Almighty and will vocally state nowhere does the Bible say Jesus is almighty.
Now that you have established the criteria and they have spoken and established their own position ask them why is Jehovah called the mighty God in the Old Testament?
They will say he is not. Have them read out loud Isa.10:20-21 tells us “Israel will rely on the LORD the Holy one of Israel… they will return to the mighty God."
Jer.32:17-18 tells us, “the mighty God whose name is the LORD (Jehovah) of hosts.”
[you have now established that Jehovah is called mighty- therefore if mighty is lesser, then Jehovah is a lesser god]
Next ask who is the Lord of Hosts? It can be shown throughout the Old Testament it is Jehovah.
Then ask- What if Jesus is called the Almighty God in the Bible, would he then be Jehovah?
They will insist this is not true - that nowhere is Jesus called the Almighty.
Have them read Rev.1:8, “I am the Alpha and Omega, the beginning and the end,” says the Lord, who is and who was and who is to come the Almighty.”
Ask them who is this that was and that is coming?
They will say the Alpha and Omega- the Almighty- is Jehovah.
You agree and read together Isa.44:6: “Thus saith the LORD the King of Israel, and His redeemer the LORD of hosts; I am the first, and I am the last; and beside me there is no God.”
Again in Isa.48:12: “Listen to Me, O Jacob, And Israel, My called: I am He, I am the First, I am also the Last.”
Then ask if the Alpha and Omega is the same as the first and the last (which is the Greek). The Old Testaments phrase “First and the last’ must be established as the same as the New Testaments “Alpha and Omega.”
Next have them read the scriptures (that are bolded) in Revelation (out loud). Throughout the Revelation the phrase “was” is in reference to Christ pointing to his death. Rev.2:8 affirms the first and the last as one “who was dead and came back to life.” Rev.1:18 says of Jesus “I am He who lives and was dead, and behold I Am alive forever more.” The same is mentioned in Rev.4:8-9 “who was and is and is to come.” This phrase is through the book - the one who died is the one coming back to earth. Rev.22:12 tells us the one who is coming is the Alpha and Omega. It is Jesus, the one who died and was resurrected who is coming, He is the same one who says “And behold, I am coming quickly, and My reward is with Me, to give to every one according to his work. "I am the Alpha and the Omega, the Beginning and the End, the First and the Last" (Rev. 22:12-13). “Surely I am coming quickly." Amen. Even so, come, Lord Jesus!” (Rev. 22:20). It is also made clear that the one coming is the almighty, who is God. “We give You thanks, O Lord God Almighty, the One who is and who was and who is to come, because You have taken Your great power and reigned.” (Rev. 11:17)
Now go back and have them read Rev.1:17-18 that shows John falling down at the feet of “the first and last,” as the one “who lives and was dead and is alive forever more.”
Ask them when did the first and the last, the alpha and omega die?
Rev 1:7 “Behold, He is coming with clouds, and every eye will see Him, even they who pierced Him. And all the tribes of the earth will mourn because of Him. Even so, Amen.
If one believes the Father is God then certainly there is no alternative but to believe the Son is also. For the Son is called by the same titles. Otherwise they must conclude that the Father is not the first or last – the almighty God.