If a Christian commits suicide, is he still forgiven?
This might seem like a perplexing question, but it does have an answer. Though the Christian who has committed suicide has committed a grave sin, he is still forgiven. But, in order to understand why a Christian who commits suicide is forgiven, we first need to understand what salvation is and what it is based upon.
Salvation is the state of being saved from God's judgment upon the sinner. The only way to be saved is to trust Jesus for the forgiveness of one's sins (John 14:6, Acts 4:12). All who do not trust Jesus alone, by faith (Rom. 5:1; Rom. 6:23; Eph. 2:8-9) are not forgiven and go to hell when they die (Matt. 25:46; John 3:18). When Jesus forgives someone, He forgives all their sins and gives them eternal life and they shall never perish (John 10:28). He does not give them temporary eternal life -- otherwise, it would not be eternal.
Salvation is not based upon what you do. In other words, you don't have to obey any Law of God in order to become saved. This is because no one is saved by keeping the Law of God (Gal. 2:21; Rom. 3:24-28). But that does not mean that you can go and sin all you want. Rom. 6:1-3 expressly condemns such action. Instead, we are saved for the purpose of purity (1 Thess. 4:7). Our salvation is strictly from God: "By grace through faith you have been saved…" (Eph. 2:8). Other than acting by faith in trusting and accepting what Jesus did on the cross, you don't do a thing (John 1:12-3) in order to become saved. Since you did not get your salvation by what you did, you can not lose it by what you do.
What about the unforgivable sin? Is that suicide? No. Suicide is not the unforgivable sin. Jesus spoke of the unforgivable sin in Matt. 12:22-32. The context is when the Pharisees accused Jesus of casting out demons by the power of the devil. Therefore, suicide is not the unforgivable sin.
Is the Christian forgiven for suicide? Yes. But suicide is not an option. We do not have the right to take our own lives. That belongs to God.