This is very powerful because in these events everything Jesus stated came true before the eyes of many.  Love your Enemies- Jesus prays for his executioners.  Those who believe will be saved - Jesus tells the theif "Assuredly I tell you today you will be with me in paradise" 

The physical punishment represents the sins we commit against God and Jesus, People needed to see what we do when we sin and to see the severity of our sins.

When Jesus cries out Father, Father why have you forsaken me"  He is also showing us the spiritual separation that sin creates between God and us his people.  it is said that the spirit of God left Jesus because of all the sins (Our Sins) that were being placed upon him.

Jesus says "It is Finished"  That is the completion of his sacrifice.  then the sky darkens and there is an earthquake.  The temple veil splits in half showing the completion and that because of Jesus there is no barrier between the father God and his people who believe what Jesus lived and died for.

Then Jesus' innocence is recognized by a roman soldier "Certainly this was a righteous man!"