Jesus Christ did not pay the debt to satan, but paid it to the Father. The Bible says "He annulled the debt we had pending by the requirements of the law" because the law was established because of sin, before there was no law, but once sin appears, God has to bring the law. And the law was through which man should be governed, but the Bible itself shows us that no one was able to comply with the law. So the debt we had pending was because we had not fulfilled any of the requirements of the law and this made us debtors before the Father, but before Satan he made us his creditors, so we were separated from the Father by sin. Then, that debt we had with the Father, became a legal right to curse us, accuse us, condemn us and prevent our lives from seeing God's prosperity and blessing.