Slide the damaged buckle piece to the end of the webbing.

Maneuver one edge of the folded webbing into the buckle piece slot.

Use needle nose pliers to grip this edge and pull the rest of the folded end through the buckle piece slot.

Discard the damaged buckle piece responsibly.

If the buckle won't come off the webbing end, it's likely not designed to be removed and requires a sewn repair.