I’ve heard the argument, which I find compelling, that Peter’s actions are proof of the Resurrection. Before the Resurrection, Peter cowardly denied Jesus three times and hid in the Upper Room. But he emerged from hiding and denial, he went to Rome, center of the pagan Empire, to bravely preach the Word even to his death by upside down crucifixion. What changed him? It is attributed to some great event that would remove all fear of death, such as seeing his Lord and Savior alive and among men.
Good perspective... but just a little off. You’ll note that the Apostles still kept themselves secluded and hidden in the Upper Room after the Resurrection. Jesus met them there at least twice by passing through locked doors. It wasn’t the Resurrection Itself that awoke the fire in Peter and the Apostles... it was the fire of the Holy Spirit on Pentacost. When you read the opening chapters of the Acts of the Apostles, note the timeline when the Apostles (specifically Peter) find their voice and courage to confront their countrymen. Their courage is kindled when they emerge after receiving the Holy Spirit as Tongues of Fire.