The link to this official Jehovah’s Witness article How to Identify Real Christians (provided by Kris) is useful as the basis for exploring how Jehovah’s Witnesses view Christians from other denominations: https://www.jw.org/en/library/books/enjoy-life-forever/section-2/lesson-18/
At first glance the article appears non-contentious then asks: SOME PEOPLE SAY: “Christians have done terrible things—how can they have the true religion?” The article concludes with this SUMMARY: Real Christians follow Bible teachings, show self-sacrificing love, and preach Bible truth.
This is where the discerning reader needs to drill down to get to the truth. This article, How False Religion Misrepresents God is more forthcoming: https://www.jw.org/en/library/books/enjoy-life-forever/section-2/lesson-13/
If God is love, why have so many evil acts been committed by religions that claim to represent him? Put simply, these religions are false; they misrepresent God.
- How does false religion misrepresent God by its teachings? False religion has “exchanged the truth of God for the lie.” (Romans 1:25) For example, most religions have not taught their followers God’s name. However, the Bible says that God’s name must be used. (Romans 10:13, 14) Some religious leaders say that when something terrible happens, it is God’s will. But that is a lie. God is never the source of evil. (Read James 1:13.) Sadly, religious lies have pushed people away from God.
- How does false religion misrepresent God by its actions? False religion does not treat people as Jehovah does. The Bible says that false religion’s “sins have massed together clear up to heaven.” (Revelation 18:5) For centuries, religions have meddled in politics, supported wars, and caused or approved the death of countless numbers of people. Some religious leaders enjoy a lavish lifestyle and demand money from their followers to pay for it. These actions prove that they do not even know God, let alone have the right to represent him.—Read 1 John 4:8.
- How does God feel about false religion? If the things done by false religion make you angry, how do you think Jehovah feels? He loves people, but he is angry with religious leaders who misrepresent him and mistreat their followers. He promises that false religion will be destroyed and “will never be found again.” (Revelation 18:21) Soon, God will put an end to all false religion.—Revelation 18:8.
- False religion does not reflect God’s love: Religions have misrepresented God in many ways. One notorious way has been their involvement in war.
SUMMARY: False religion has misrepresented God by means of its false teachings and terrible practices. God will destroy false religion.
Jehovah’s Witnesses believe this will happen at Armageddon and only dedicated, faithful and obedient Jehovah’s Witnesses will survive. They believe virtually every person who has died before Armageddon will be resurrected with a physical body and be given an opportunity to be saved during the millennial reign of Christ Jesus, from heaven, over the inhabitants of a paradise earth.
For the avoidance of any doubt, it is important to understand that Jehovah’s Witnesses believe every Trinitarian Christian denomination is part of the Antichrist:
What about today? People and organizations making up the antichrist still oppose Christ and his teachings. They deliberately spread lies and deceptions with the intent of confusing the identity of the Father, Jehovah God, and of His Son, Jesus Christ. We have good reason to beware of such religious deceptions. Let us look at two examples.
For centuries, the churches propagated the doctrine of the Trinity, claiming that the Father and the Son are part of the same entity. The antichrist thus shrouds in mystery the identity of Jehovah God and Jesus Christ. This mystery hinders sincere people from imitating Jesus Christ and drawing close to God, as the Bible encourages them to.—1 Corinthians 11:1; James 4:8.
The churches add to the confusion by promoting the use of Bible translations that omit God’s personal name, Jehovah, from the text. They do this despite the fact that the name Jehovah occurs some 7,000 times in the original text of the Bible. The result? The identity of the true God becomes even more shrouded in mystery.
For centuries, the antichrist has kept millions in spiritual darkness. But by studying God’s Word, the Bible, we are able to learn the true identity of the antichrist and be set free from the antichrist’s religious lies and deceptions.—John 17:17.
Those are some (but not all) of the essential features of a true follower of Christ according to Jehovah’s Witnesses. True followers of Christ denounce the Trinity, actively promote the name Jehovah, and they will have nothing to do with “Christendom” because of “its false teachings and terrible practices. God will destroy false religion.”
Jehovah’s Witnesses believe they, and only they, have the “truth” and that they are Jehovah’s sole appointed earthly organisation. Even Christian denominations that reject the Trinity doctrine fail because they do not promote the name Jehovah in their Bibles, and are not baptised Witnesses of Jehovah. They are all, without exception, part of “false religion”, soon to be destroyed at Armageddon.
This link provides access to other related articles: https://www.jw.org/en/search/?q=antichrist