The cross doesn't cover "everything". It is possible to fall short of grace.
Heb 12:15; See to it that no one
comes short of the grace of God; that no root of bitterness springing up causes trouble, and by it
many be defiled;
Also there are two unforgivable sins.
Matt 12:31; "Therefore I say to you, any sin and blasphemy shall be forgiven people, but blasphemy against the Spirit shall not be forgiven.
Matt 12:32;
"Whoever speaks a word against the Son of Man, it shall be forgiven him; but whoever speaks against the Holy Spirit, it shall not be forgiven him, either in this age or in the age to come.
Luke 12:10; "And everyone who speaks a word against the Son of Man, it will be forgiven him; but he who blasphemes against the Holy Spirit, it will not be forgiven him.
-----------
Rev 14:9; Then another angel, a third one, followed them, saying with a loud voice, "
If anyone worships the beast and his image, and receives a mark on his forehead or on his hand,
Rev 14:10; he also will drink of the wine of
the wrath of God, which is mixed in full str
ength in the cup of His anger; and he will be tormented with fire and brimstone in the presence of the holy angels and in the presence of the Lamb.