In past threads here at AF (see especially the early threads under the Monarchy of God the Father label), I have presented solid, irrefutable evidence(s) that certain theological titles used in the New Testament have been reserved for God the Father alone—e.g. "one God", "the only true God", "the only God", "the only wise God" and "the God of Abraham, Isaac and Jacob"—I would now like to add two more: "the Almighty" and "the Lord God".
The phrase/title "the Almighty" (Greek: ὁ παντοκράτωρ) is used only 10 times in the NT, and all but one, are found in the Book of Revelation: 2 Cor. 6:18; Rev. 1:8; 4:8; 11:17; 15:3; 16:7, 14; 19:6, 15; 21:22.
As for the phrase/title "the Lord God" (Greek: κύριος ὁ θεὸς), it is found only 12 times in the NT: Mark 12:29; Luke 1:32; 1:68; Acts 2:39; 3:22; Rev. 1:8; 4:8; 18:8; 19:6; 21:22; 22:5, 6.
I find it interesting that the two phrases/titles are found together in 4 of the above verses: Rev. 1:8; 4:8; 19:6; 21:22. Of note in particular, is Rev. 21:22, where we read:
And I saw no temple therein: for the Lord God the Almighty, and the Lamb, are the temple thereof. (ASV) (Greek: Καὶ ναὸν οὐκ εἶδον ἐν αὐτῇ, ὁ γὰρ κύριος ὁ θεὸς ὁ παντοκράτωρ ναὸς αὐτῆς ἐστιν, καὶ τὸ ἀρνίον.)
In the above verse, we have a distinction being made between two separate persons: "the Lord God the Almighty" and "the Lamb"; the former being God the Father, and the latter Jesus Christ, the Son of God.
Now, some commentators have attempted to designate Jesus Christ as the person who is speaking in Rev. 1:8, but this is a huge 'stretch'. Please note the following:
To the "amen" of Christ and the community is added the direct voice of κύριος ὁ θεὁς (kyrios ho theos, the Lord God). Only here and in 21:5-6 does God speak directly... (Dr. Grant R. Osborne, Baker Exegetical Commentary of the New Testament - Revelation, p. 71.)
In footnote #31 on the same page, Dr. Osborne adds:
While some (Walvoord 1966: 40; perhaps Carid 1966: 19) have argued that this is Christ rather than the Father (due to the centrality of Christ in the context), the use of OT designations for God ("LORD of Hosts" was a favorite OT title) and the repetition of the title for God in v. [sic; v. should read ch.] 4 make it more likely this refers to God the Father.
Only here [Rev. 1:8] and in 21:5 does God [the Father] himself speak. (Dr. Robert H. Mounce, The Book of Revelation, p. 73.)
A careful distinction should be drawn between the Father as κύριος ὁ θεὁς (= Yahweh Elohim*)—a designation never used of Christ in the NT—and Christ as ὁ κύριός μου καὶ ὁ θεός μου. While distinct from Yahweh, Christ shares his status and his nature. (Dr. Murray J. Harris, Jesus as God, footnote 86, p. 123.)
Grace and peace,