When we consider the crucifixion it is about Jesus' arrest, trial, suffering and carrying the cross. It is appropriate that the story is all about him. However, there were two others who shared the moment.
The climax of the Roman soldiers' brutality came when Jesus was forced to wear a painful crown of thorns. They pretended to treat him as a king but the truth was they despised him.
In the trial of Jesus the Pharisees recruited some nameless individuals to falsely accuse Jesus. Of course Jesus was guilty of nothing so all accusations were false.
Peter is known for his impulsive behavior, his bold proclamations and willingness to die with Jesus if need be. That is what makes his denial so tragic.