Unitarians are those who, like the Trinitarians, believe that there is only one God. However, unlike the Trinitarians the Unitarians teaches that God is only one person opposed to three persons of the one true God.
The most well known Unitarian churches are the Jehovah's Witnesses which began in the late 1800's by Charles Taze Russel who begun leading bible studies and soon begun his own church.
The gospel of the Jehovah's Witnesses centers around their eschatology, that God will soon bring judgment, ending wars and other sources of suffering and evil, and restore all things. Charles Taze Russell, was a man God raised in the midst of the corrupted and hypocritical mainline churches and restored biblical truths forgotten by them. He established the Watchtower and Tract Society (which became their HQ), and the Jehovah's Witnesses came to be.
They believe that their church is the one, true, church. No one can be saved outside of their organization. This rhetoric is the most common thing in cult groups.
Other beliefs of their are as follows. They believe that only the 144,000 will be in heaven while everyone else who are obedient will be in paradise. Not only that, they believe in Annihilationism: that the damned will not suffer in Hell forever but will only die and be no more.
Returning to God, the Jehovah's Witnesses claimed that Jesus is Michael the Archangel and the Holy Spirit is God's active force, in their opposition to the biblical teachings of the Trinity made their own bible version called the, "New World Translation", and through it deliberately altered bible passages that most strongly supports the Trinity, specifically the deity of Christ, and changed them.
For example, in John 1:1 when it says "... and the Lord was with God, and the word was God", their version reads "and the word was with God and the word was a God". They added the article "...a..." to deliberately demote Christ into a lesser, created being.
Other altered passages as follows:
In Colossians 1:15-16 where it says Christ made all things, their versions says "...all other things...". then in Hebrews 1:8 where it says "... let all the angels worship him", but in their translation: "... let all the angels of God do obeisance to him" turning the word "... worship..." to "... obeisance...." which means to bow down.
This church is a heretical cult group, which has the last belief every cult has: that salvation has to be earned, contrary to scripture.