The doctrine of God and Christology is not based on one proof text. There is probably no doctrine we could prove to you from one verse to your satisfaction. When JWs are given a verse about the trinity or Deity of Christ, they pit another verse against it to create a contradiction. This is why we cannot proof text one verse out of context. It is cumulative evidence of all verses that show the triune understanding since it is progressive revelation from Old Testament monotheism to fulness of Christ in incarnation (Heb. 1:1-3) and further detail on the Holy Spirit in Jn. 14-16, etc.
The WT gives simplistic answers to more complex issues. They have purged intellectuals from their midst and usually attract uneducated people who will not think critically, but want the WT to think for them (and the WT insists that they not be questioned, even if wrong). You may be an ex-JW, but you still have some of the root issues?
Matthew 28:18-20 singular name and mention of 3 personal distinctions (in the name of the Father God, Michael the Archangel, and the active force is NOT what it says!) is a start.
Jn. 1:1 The first clause shows that the Word was eternally preexisting when there was a beginning to creation (Gk. was=imperfect, continuous tense; contrary to JW Arianism). The Word was with God (Gk. pros/face to face). Thus, He is personally distinct from the Father/Gk. ho theos, but Jesus is also called ho theos elsewhere (contrary to modalism/Sabellianism/oneness). The last clause (see KIT, not NWT a god) is qualitative, anarthrous (without definite article) and shows that the Word is of the nature of God (but not the person of the Father; if modalism was true/Jesus=Father, then the grammar would be different). We know from the Shema (Deut. 6:4) and many other verses that there is one true God by nature. If Jesus was a god, this would be polytheism unless he is a false god. This verse alone supports the triune understanding even though the Holy Spirit is not mentioned. Other passages in John establish His Deity and personality (impersonal force is gross error by WT). Jn. 1:14 identifies the Logos/Word as Jesus Himself, God with a face, God in the flesh.
So, I can give a list of verses that say that there is one true God, YHWH. There are not many gods (contrary to Mormonism/Hinduism). We can also find verses that say that the Father is God, the Son is God (Deity of Christ), and the Spirit is God. We can also find verses that show the personal distinction between F, S, HS (the Father is not the Son, the Son is not the Spirit, the Spirit is not the Father). The only way to reconcile all of the biblical date is a triune (compound unity) understanding.
The ex-JWs who come to this understanding often see that Jesus is Jehovah even if they do not understand the trinitarian implications. Others see the personality of the Spirit (an even easier concept). This eventually leads one to a trinitarian view, the biblical, historical, orthodox view of Christianity from biblical times, ff.
The WT booklet on should you believe in the trinity is full of misquotes (I have the booklet and the photocopies of every page in outside sources that they quote), straw men arguments, etc. It can be systematically refuted line by line.
Here is a link to help understand the trinity. (if it says trinity proof texts, you can click on the verse in the article for a detailed explanation of the verse). I would believe it based on the two verses I gave you, but a definitive case will be based on all relevant verses. There are few doctrines that can be established in a true, balanced way by one verse, so your request is not reasonable. This is the problem with cults that have a conclusion and then they tack on verses out of context to try to prove their point (can make Bible say all kinds of things it did not intend using this method). We need to do sound exegesis and establish a biblical theology based on extended passages. When Raymond Franz looked at Christendom's commentaries at Bethel for research, he saw how they kept things in context of paragraphs leading to right conclusions. This contrasted with WT books that had a heading and then took isolated verses out of context (e.g. Jn. 14:28; Eccl. 9:5, etc.) to prove the point. This is shoddy scholarship/eisegesis (reading meaning back in from bias vs pulling it out of text=exegesis).
I can deal with the few Arian proof texts from a trinitarian view, but can WT deal with dozens or hundreds of Deity/trinitarian verses? No, so they mistranslate these passages in NWT so average JW will not realize the Bible does not support WT since few bother to research or learn Gk., etc.
If you have specific questions, I will be happy to 'reason from Scripture' like a Berean with you. If you want to refer to WT arguments or literature, I am not afraid of that (even though you are not JW, but how much of your indoctrination is affecting your thinking still?).