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Although many try, you can't square the loving forgiving God we see in Jesus to the vengeful God that is sometimes portrayed in the OT. It can't be done. That does not mean that we can't find the loving God in the pages of the OT as well.
What do you do with the NT passages that describe Jesus as that vengeful God?
(Oh I'm sure I know: you tell yourself they were written by people who hold opinions you don't like so therefore they must be false. Oh well.)
2 Thessalonians 1:6-9 Seeing it is a righteous thing with God to recompense tribulation to them that trouble you; And to you who are troubled rest with us, when the Lord Jesus shall be revealed from heaven with his mighty angels, In flaming fire taking vengeance on them that know not God, and that obey not the gospel of our Lord Jesus Christ: Who shall be punished with everlasting destruction from the presence of the Lord, and from the glory of his power;
Revelation 14:9-10 And the third angel followed them, saying with a loud voice, If any man worship the beast and his image, and receive his mark in his forehead, or in his hand, The same shall drink of the wine of the wrath of God, which is poured out without mixture into the cup of his indignation; and he shall be tormented with fire and brimstone in the presence of the holy angels, and in the presence of the Lamb....