Peter preached Jesus crucifixion as a murder indictment. Examples were Acts 2:36, where Peter says, "... Jesus, whom ye crucified ...." Peter also says in Acts 3:14-15, "But ye denied the Holy One ... and killed the Prince of life ...." Then in Acts 5:30 he says, "... Jesus, whom ye slew and hanged on a tree." Finally Stephen, who also preached Peter's gospel, told the Jews in Acts 7:52, "Which of the prophets have not your fathers persecuted? and they have slain them which shewed before of the coming of the Just One; of whom ye have been now the betrayers and murderers ...."
Until the conversion of Saul/Paul, the crucifixion had been pointed out by the 12 apostles to their intended audience, the Jews, as something to be ashamed of and repented of.
Only after the ascended Jesus revealed the mystery of the gospel of grace to Paul (Ephesians 3:3-5), then all of us Gentile Christians, together with Paul, can look back to the crucifixion and cry: "He loved me and gave Himself for me!" Jesus was not murdered, instead he laid down his life for ME.
Indeed, the follow non-exhaustive list of verses written by Paul that testified to the importance of the cross in the divine exchange is as follows
Romans 3:25 (NLT) For God presented Jesus as the sacrifice for sin. People are made right with God when they believe that Jesus sacrificed his life, shedding his blood. This sacrifice shows that God was being fair when he held back and did not punish those who sinned in times past
1 Corinthians 1:18 New Living Translation (NLT) 18 The message of the cross is foolish to those who are headed for destruction! But we who are being saved know it is the very power of God.
Galatians 6:4 New Living Translation (NLT) As for me, may I never boast about anything except the cross of our Lord Jesus Christ.
Colossians 1:20 (NASB) and through Him to reconcile all things to Himself, having made peace through the blood of His cross; through Him, I say, whether things on earth or things in heaven.
Colossians 2:14 (NIRV) He wiped out the written Law with its rules. The Law was against us. It opposed us. He took it away and nailed it to the cross.
Peter was not preaching the same gospel of grace as the Apostle Paul did. As an example, I can imagine if Peter did preach the same message about the cross as Paul did, and if he did mentioned Colossians 2:14. his Jewish listeners would very likely stone him on the spot, given how zealous they are for the law. ( Acts 21:20)
But he didn't have to preach that since Galatians 2 clearly stated
7 But contrariwise, when they saw that the gospel of the uncircumcision was committed unto me, as the gospel of the circumcision was unto Peter;
8 (For he that wrought effectually in Peter to the apostleship of the circumcision, the same was mighty in me toward the Gentiles
9 And when James, Cephas, and John, who seemed to be pillars, perceived the grace that was given unto me, they gave to me and Barnabas the right hands of fellowship; that we should go unto the heathen, and they unto the circumcision.
In the Gospel of the Kingdom, which is for the circumcised Jews, there is no need for them to believe that Jesus died for their sins and rose again as a sign that they are now justified in the eyes of God.
All they need to do is to acknowledge that Jesus is the promised Messiah and King sent to them. As the Gospel of John concluded in ch 20, remember he was one of the 3 apostles who agreed to confine their ministry to only the Jews,
29 Jesus saith unto him, Thomas, because thou hast seen me, thou hast believed: blessed are they that have not seen, and yet have believed.
30 And many other signs truly did Jesus in the presence of his disciples, which are not written in this book:
31 But these are written, that ye might believe that Jesus is the Christ, the Son of God; and that believing ye might have life through his name.