What could be more unforgivable than to sell a brother into slavery? Yet Joseph interprets his life from another point of view.
Genesis 45:4-7 ESV
So Joseph said to his brothers, “Come near to me, please.” And they came near. And he said, “I am your brother, Joseph, whom you sold into Egypt.  And now do not be distressed or angry with yourselves because you sold me here, for God sent me before you to preserve life.  For the famine has been in the land these two years, and there are yet five years in which there will be neither plowing nor harvest.  And God sent me before you to preserve for you a remnant on earth, and to keep alive for you many survivors.
The Joseph account makes it clear several times that the events of their lives were orchestrated by God, for a larger purpose than what they ever had in mind. This makes a high theology of “providence”, that God is ordering the events of this world, including our freely made and even evil choices, into a good outcome.
See what Paul said on this in Acts 17:24-28