A simple reasoning
According to non trinitarians Jesus came after the Father. So Father is the first being and Jesus is the second being in this universe.
Father claims “I am the first, and I am the last;” and Jesus also claims “I am Alpha and Omega, the beginning and the end, the first and the last.”
Is it not a lie; When Jesus being the second person in this universe and first being God the Father how can He claim that He is first like God the Father.
Also God the Father claims “beside me there is no God.”; Bible says that Jesus is God.
Where is the error here. Is it with Trinity or non trinity?
Adventist Apology Site 
Wow, now i understand and I can now confuse the J. Witnesses.
“For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him.” “Him hath God exalted with his right hand to be a Prince and a Saviour, for to give repentance to Israel, and forgiveness of sins.” A complete offering has been made; for “God so loved the world, that he gave his only-begotten Son,”– not a son by creation, as were the angels, nor a son by adoption, as is the forgiven sinner, but a Son begotten in the express image of the Father’s person, and in all the brightness of his majesty and glory, one equal with God in authority, dignity, and divine perfection. In him dwelt all the fullness of the Godhead bodily.
ST, May 30, 1895
The Eternal Father, the unchangeable one, gave his only begotten Son, tore from his bosom Him who was made in the express image of his person, and sent him down to earth to reveal how greatly he loved mankind. RH, July 9, 1895