"Father, forgive them, for they do not know what they are doing." (Luke 23:34)
Did God answer this prayer of Jesus? Of course, God forgave those who tortured and killed His Son.
What sin then will be left unforgiven?
"He is the atoning sacrifice for our sins, and not only for ours but also for the sins of the whole world." (1 John 2:2)
"This is love: not that we loved God, but that he loved us and sent His Son as an atoning sacrifice for our sins." (1 John 4:10)
"And we have seen and testify that the Father has sent His Son to be the Savior of the world." (1 John 4:14)
Jesus is not the Savior of humanity if He fails to save even one human!
"For the grace of God has appeared, bringing salvation to all people, instructing us to deny ungodliness and worldly desires and to live sensibly, righteously, and in a godly manner in the present age, looking for the blessed hope and the appearing of the glory of our great God and Savior, Christ Jesus, who gave Himself for us to redeem us from every lawless deed, and to purify for Himself a people for His own possession, eager for good deeds. These things speak and exhort, and rebuke with all authority." (Titus 2:11-15)