The sinner must be convicted of his guilt, corruption, and ____ before God.

The correct answer is sinfulness. Conviction of one's sinfulness is a crucial step in the process of realizing the need for salvation and reconciliation with God. This conviction leads the individual to recognize their sinful nature and the inherent separation from God that it causes. Understanding one’s sinfulness highlights the understanding that apart from God's grace, one is unable to attain righteousness.

While the other options touch on important aspects of the Christian faith, they do not directly address the fundamental recognition of personal sin that leads to repentance and transformation. Redemption and forgiveness pertain to the solutions and outcomes of acknowledging one's sinfulness, while offensiveness, though it may reflect how sin impacts one’s relationship with God and others, does not encapsulate the essence of recognizing one's need for change and salvation as effectively as sinfulness does. Thus, recognizing one's sinfulness is integral to the theological understanding of human nature and the necessity of grace in Christian doctrine.