Found this article helpful:
https://bible.org/article/jehovahs-witnesses-and-trinity
...The Alpha and the Omega
As I have witnessed to many Jehovah’s Witnesses, I have found some verses that work most effectively in proving the deity of Christ. Here are two of my favorite combination of verses.
The first verse is Revelation 1:8. I am reading from the Jehovah’s Witness Bible, and it reads, “I am the Alpha and the Omega,” says Jehovah God. Ask the Witness, “What does Alpha and Omega mean?” They’ll reply,”The beginning and the end.” Then ask them, “How many Alphas and Omegas can you have?” They’ll answer, “Only one.” Make sure you get this point across, there is only one Alpha and Omega.
Then turn to Revelation 22:12-13 which says, “Look I am coming quickly, and the reward I give is with me....I am the Alpha and the Omega, the first and the last, the beginning and the end.” Ask the Witnesses, “Who do you say the Alpha and Omega is?” They will say, “Jehovah.” Now take a careful look. The Alpha and Omega in verse twelve is coming quickly. Let’s see who is speaking in verse twelve.
Look at verse sixteen, “I Jesus, sent my angel to bear witness to you people of these things for the congregations. I am the root and the offspring of David, the bright morning star.” It is Jesus speaking in verse twelve. If there is any doubt go to verse 20 which says, “He that bears witness of these things says, ‘Yes; I am coming quickly’ Amen come Lord Jesus.” So it is clear that the Alpha and the Omega in verse twelve is Jesus. Here is a strong proof text that Jesus is God because both Jehovah and Jesus are called the Alpha and the Omega.
Another pair of verses that are effective when used together are Isaiah 44:6 and Revelation 1:17-18. Isaiah 44:6 says, “This is what Jehovah has said, ‘The king of Israel and the Repurchaser of him, Jehovah of armies, I am the first and I am the last.’“ Ask the Witnesses how many firsts and lasts can you have? It’s obvious to anyone you can only have one first and one last. Ask them, “Who is the first and the last?” They will say, “Jehovah.” Now turn to Revelation 1:17-18 which says, “Do not be fearful; I am the First and the Last, and the living one; and I became dead but look! I am living forever.” Who is speaking here? Obviously, it is Jesus for He died but is now alive, and guess what? He is called the First and the Last. Here again we see Jesus is God.
These are my favorite verses, and I have never had Witnesses refute these arguments. Remember, the Witnesses at your door won’t convert right then and there. The key is to get them to start thinking and questioning the organization, and down the road, maybe in several years, they will seek answers and that will lead them out of the organization. Don’t give up or be discouraged when sharing with Witnesses. Though they may be rude and show no signs that they are thinking, the Word of God is powerful and is working in their hearts even if we can’t see it.