Matthew 27:44 and Mark 15:32 mention the two men crucified with Jesus, but make no mention of one of them proclaiming faith in Jesus as told in Luke. In fact, in Matthew and Mark it is said that both men were ridiculing Jesus.
Mat 27:43 He trusted in God; let him deliver him now, if he will have him: for he said, I am the Son of God.
Mat 27:44 The thieves also, which were crucified with him, cast the same in his teeth.
Mar 15:31 Likewise also the chief priests mocking said among themselves with the scribes, He saved others; himself he cannot save.
Mar 15:32 Let Christ the King of Israel descend now from the cross, that we may see and believe. And they that were crucified with him reviled him.
The thieves did appear to go against Jesus, and at this point the Pharisees, scribes, as well as other Jews, were going against Jesus, which the Romans would of been against Jesus, with none of them believing Jesus is the Messiah, and who He claimed for He did not come down from the cross, but looked at Him as defeated not understanding the plan of God.
Luk 23:39 And one of the malefactors which were hanged railed on him, saying, If thou be Christ, save thyself and us.
Luk 23:40 But the other answering rebuked him, saying, Dost not thou fear God, seeing thou art in the same condemnation?
Luk 23:41 And we indeed justly; for we receive the due reward of our deeds: but this man hath done nothing amiss.
Luk 23:42 And he said unto Jesus, Lord, remember me when thou comest into thy kingdom.
Luk 23:43 And Jesus said unto him, Verily I say unto thee, To day shalt thou be with me in paradise.
And in these scriptures one went against Jesus, and one did not go against Jesus.
Mat 27:50 Jesus, when he had cried again with a loud voice, yielded up the ghost.
Mat 27:51 And, behold, the veil of the temple was rent in twain from the top to the bottom; and the earth did quake, and the rocks rent;
Mat 27:52 And the graves were opened; and many bodies of the saints which slept arose,
Mat 27:53 And came out of the graves after his resurrection, and went into the holy city, and appeared unto many.
Mat 27:54 Now when the centurion, and they that were with him, watching Jesus, saw the earthquake, and those things that were done, they feared greatly, saying, Truly this was the Son of God.
After Jesus died and this happened then some believed Jesus was the Son of God, and telling the truth, but the thief talked to Jesus before He died, and Jesus talked to Him.
But it does show that when Jesus was on the cross that some that went against Jesus could of changed their mind and then believed, and could happen before He died.
Mar 15:25 And it was the third hour, and they crucified him.
Mar 15:32 Let Christ the King of Israel descend now from the cross, that we may see and believe. And they that were crucified with him reviled him.
Mar 15:33 And when the sixth hour was come, there was darkness over the whole land until the ninth hour.
Mar 15:37 And Jesus cried with a loud voice, and gave up the ghost.
Jesus hung on the cross for 6 hours before He died, which all that He said was not recorded in scriptures, which I am sure that He had a lot more to say while He was alive on the cross.
And Jesus was alive for 3 hours on the cross and during that the time the thieves went against Jesus, but we do not know when the thieves went against Him during that time period, for they could of went against Him at the first hour leaving 2 hours to be able to speak and reason with them, as well as other people at the cross.
So one of them might of changed his mind concerning Jesus and accepted Him.
Sometimes scriptures of the different Gospels do not include some things as other the other Gospels for they did not record it while another recorded it.
So Matthew and Mark recorded the thieves went against Jesus, but did not include that one of them changed his mind having ample time of Jesus being alive on the cross to still speak concerning the truth.
Where Luke did not record the incident of both thieves going against Jesus, but one going against Him, and another accepting Him leaving out the 2 thieves going against Him.
And John does not mention the 2 thieves, and does not mention the veil being ripped, and the centurion and others saying this is truly the Son of God.
Jesus was alive for 6 hours on the cross and He would of said more than what was recorded for He would of kept preaching the truth until His dying breath, and even said Father forgive them for they know not what they do, and everyone would of heard Jesus speaking including the 2 thieves, and something must of caught the attention of the one thief and he changed his mind and accepted Jesus, but at the first he was going along with the crowd, and maybe some in the crowd started to believe and help to influence him.
Another example.
Matthew.
Mary Magdalene, and Mary went to the grave.
Went to tell the disciples, and met Jesus on the way.
No mention of them telling the disciples, although they did.
Mark.
Mary Magdalene, and Mary, and Salome went to the grave.
Went to tell the disciples, Jesus appeared to Mary Magdalene.
Told the disciples.
Luke.
Mary Magdalene, and Mary, and Joanna, and other women went to the grave.
No mention of meeting Jesus, but they did.
Told the disciples.
Peter ran to the grave.
John.
Mary Magdalene went to the grave.
Went and told Peter and John, but no mention of meeting Jesus along the way, but she did, and no mention of telling the other disciples but Peter and John, but she did.
Peter and John ran to the grave.
And then Mary was at the grave so she came back to the grave and saw Jesus, but no mention in the other Gospels.
So not all Gospels are going to tell the same story and give all the details as each other, although they could with some.
The 2 thieves that went against Jesus, one of them changed his mind, but Matthew and Mark record that they went along with the crowd and went against Him at the first, but Luke records that one of them accepted Jesus, and John does not mention the 2 thieves, and no mention of the earthquake, the veil being ripped, and the centurion and others saying this is the Son of God after Jesus died.