Sinners will not enter the kingdom of God. We need forgiveness of our sins before we can enter into the kingdom of God. God is a holy and righteous God. He will not condone any iniquity. The Bible lets us know that there shall be nothing that defiles be found in heaven. So, sinners and in fact, everyone of us needs to receive forgiveness of sins.
We should also understand that we must forgive those who sin against us. We must not allow offenses in our hearts against others. Anyone who sins against us must be forgiven by us. We should always be forgiving. There is no offense which a brother or a sister does to us that we cannot forgive. Jesus Christ told us that we must follow someone who offends us 70×7 times. That is a whole lot. That means that we must forgive at all times.
Looking at the word of God, we will discover that there are grievous sins. The Bible tells us that we should not commit such sins. It tells us of sins in which there is no sacrifice of forgiveness anymore. The Lord Jesus Christ told that blasphemy against the Holy Spirit shall not be forgiven. So, as christians we need to be careful with the way we behave so that we do not commit the unpardonable sins.