If I were the only person who needed redemption, would Christ still have gone to the cross?
Yes. The atonement is personal and complete: if you or I had been the only person living, Christ would still have gone to the cross to purchase our redemption. God Himself paid the penalty for all our sin, and saving faith rests in that finished act, not in works.
Les teaches that if you or I had been the only person living, Christ would still have gone to the cross to purchase our redemption. He explains this in the context of a concerted faith and trust in God's very act, that God Himself paid the penalty for all our sin. When a person believes that with all their heart, knowing He is alive and His Word is true, God sees that faith as salvation. As Romans 4 makes plain, Abraham was not saved by works but by faith: he believed God, and God accounted it unto him as righteousness.