For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
A true Christian according to the bible is one who has believed and received the free gift of eternal life.
First John 5:13 These things have I written unto you that BELIEVE on the name of the Son of God, that ye may KNOW YE HAVE ETERNAL LIFE.
Romans 6:23 For the wages of sin is death, physical death, but the GIFT of God is eternal life through Jesus Christ our Lord.
The GIFT of God is eternal life, paid for in full by His one blood sacrifice for the sins of the whole world. Since He paid tor the sins of the whole world, then He paid for all my sins. First John 2:2.
Romans 4:7-8. Since He paid my sin debt in full, I can not go to hell because I have no sins to pay for. John 3:18.
The thief on the cross did nothing but believe Jesus was the Son of God and was saved the instant he changed his mind. Repented, and believed on Jesus.
John 3:16 For God so loved the world, that HE gave HIs only begotten Son, Jesus, that WHOSOEVER believeth in Him, should not perish, but HAVE EVERLASTING LIFE.
The GIFT of God is eternal life. We receive the free gift by faith alone in Jesus alone apart from anything else. Nothing else can save sinners except what He did.
Nothing we do could save us. We have a sin debt we owe God and have no way to pay our debt. Jesus paid the debt and set us free. Since it is a free gift, we have nothing to boast in. He paid it all and we paid 0.
Romans 3:26-28 For He is the just and the justifier of them that BELIEVE in Jesus. Where is boasting then? It is excluded. By what law? By the law of works? Nay, but by the Law of FAITH. Therefore we conclude that a man is justified by FAITH, apart from the deeds of the law.
John 3:18 Believers can no longer be condemned to hell. Unbelievers are condemned already because they have not believed on the name of the Son of God
John 6:47 Verily, verily, I say unto you, he that believeth on me HATH EVERLASTING LIFE.
Since it is everlasting life it lasts forever. The GIFT of God is eternal life. If you have eternal life today, then you will still have it 100 years from now because it is eternal.
So, a Christian is one who has accepted Jesus as the only way to be saved from hell and go to heaven whenever we die.
John 3:18 Believers have eternal life. John 6:40 And this is the will of Him who sent me, that ALL that seeth the Son, and believeth on Him, may have everlasting life, and I will raise him up on the last day.
Ephesians 1:13-14 is our guarantee of eternal life. Ephesians 4:30 And grieve not the Holy Spirt in whom ye are SEALED UNTO THE DAY OF REDEMPTION.
The greatest gift a person could ever receive is the free GIFT of Eternal life. Paid in full by the GIVER.