Question: "How bad can a Christian sin?"
Answer: Christians continue to sin after they are saved – we will not be completely free from sin until we die or Jesus comes back. However, becoming a Christian results in a changed life (2 Corinthians 5:17). A person will go from producing the acts of the flesh (Galatians 5:19-21) to displaying the fruits of the Spirit (Galatians 5:22-23), as the indwelling Holy Spirit has more and more control over his life. This change does not happen instantly, but it does happen over time. If a person does not demonstrate a changed life, he/she is likely not a genuine believer. Christians can commit grievous sins. History is filled with Christians (or those who claim to be Christians) committing terrible crimes. Jesus died for these sins as well. All the more reason not to commit them!
In 1 Corinthians 6:9-11, the Apostle Paul describes the kind of sinful lifestyles believers are saved from. Verse 11 says, “And that is what some of you were. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God.” Notice the word “were.” Believers used to be like the things listed in verses 9-10, but they are not like that any longer. Can a person who is an adulterer, drunkard, homosexual, child abuser, etc. be saved? Yes. Is a person who lives a life of continual sin a believer? No. When we become Christians, our lives will change. Anyone who is living a sinful lifestyle and claims to be a Christian is either lying, is self-deceived, or really is a believer who is going to experience God’s judgment and discipline (Hebrews 12:5-11).
The difference between a sinning unbeliever and a sinning believer is that one loves his sin while the other hates it. The believer who stumbles in his walk with the Lord regrets it, confesses it, wishes to never do it again and seeks to appropriate God’s power and grace to avoid it. He doesn’t consider how much he can sin and still be considered a Christian. Rather, he considers how he can avoid even the appearance of sin in the future.