How do we know that Christ has destroyed the power of sin?

The power of sin is destroyed through the work of Christ, as stated in Romans 6:6. When Paul articulates that our old man is crucified with Christ, he means that the reigning power of sin is effectively nullified through His death. This means that believers are liberated from the bondage and authority that sin once held over them. Further confirmation of this can be found in Colossians 2:14-15, where it describes how Christ blotted out the ordinances against us, effectively triumphing over spiritual powers and rendering them powerless for those who trust in Him.