Crucifixion is one of the most painful methods of execution ever devised. Here is an article that describes Christ’s crucifixion and also the suffering he experienced before it.
He knew before his arrest what he would endure. Is it any wonder that he prayed that God would enable him to avoid it if that were possible?
And he withdrew from them about a stone’s throw, and knelt down and prayed, saying, “Father, if you are willing, remove this cup from me. Nevertheless, not my will, but yours, be done.” And there appeared to him an angel from heaven, strengthening him. And being in agony he prayed more earnestly; and his sweat became like great drops of blood falling down to the ground.
He wanted to avoid the pain of being crucified but he wanted even more to do God’s will. His death was the only way human sin could be atoned for, so in the end he submitted to being put to death.
The physical pain wasn’t the only form of suffering Jesus experienced while he was on the cross.
Now from the sixth hour there was darkness over all the land until the ninth hour. And about the ninth hour Jesus cried out with a loud voice, saying, “Eli, Eli, lema sabachthani?” that is, “My God, my God, why have you forsaken me?”
Why would Jesus think God had forsaken him? Probably because God had forsaken him. Jesus died to atone for our sins. That meant that our sins had to be placed on him.
He himself bore our sins in his body on the tree, that we might die to sin and live to righteousness. By his wounds you have been healed.
1 Peter 2:24
The prophet Habakkuk tells us how God views sin.
You are of purer eyes than to see evil
and cannot look at wrong.
While Jesus was bearing our sins, God’s holiness required that God turn his back on him and have no contact with him whatever. We can’t understand how much Jesus suffered from that rejection because being separated from God by sin is the normal condition of the human race. Jesus, on the other hand, had enjoyed perfect fellowship with the Father for all eternity. Being separated from God was much more painful for him than the physical pain he experienced. In fact, it was probably the pain of separation rather than physical pain that made him ask the Father if there was any way to avoid the cross.