“I am Alpha and Omega, the beginning and the ending, saith the Lord, which is, and which was, and which is to come, the Almighty.” (Rev 1:8 KJV)
Alpha and Omega are the first and last letters of the Greek alphabet. The phrases “Alpha and Omega”, “the first and the last”, and “the beginning and the ending” are different ways to show the completeness of identity of Jesus. Jesus is all the fullness of the Godhead bodily.
“9 For in him dwelleth all the fulness of the Godhead bodily.
10 And ye are complete in him, which is the head of all principality and power:”
(Col 2:9-10 KJV)
Jesus is not a part of God, or a secondary Deity. He is the One God that is from everlasting to everlasting. He is Lord of all lords, King of all kings. He truly has all power.
“And Jesus came and spake unto them, saying, All power is given unto me in heaven and in earth.” (Mat 28:18 KJV)
And He truly is Almighty.
“15 Which in his times he shall shew, who is the blessed and only Potentate, the King of kings, and Lord of lords;
16 Who only hath immortality, dwelling in the light which no man can approach unto; whom no man hath seen, nor can see: to whom be honour and power everlasting. Amen.”
(1Ti 6:15-16 KJV)