The story of  the woman caught in adultery is the clincher for the Goodness of God

The Pharisees quite correctly stated that the Old Testament God was clearly against the woman caught in adultery.   The Torah in Leviticus 20:10 states that the Woman caught in adultery had the death sentence on her.

There were no escape clauses - the penalty for adultery under the Law of Moses was death.

But Jesus gets her off.  

Not only that, but it is clearly stated (John 8:28) that it is God the Father's idea!

Then Jesus said to them, When you have lifted up the Son of Man, then you shall know that I AM, and that I do nothing of Myself, but as My Father has taught Me, I speak these things.

At the time he rescued the Woman there was no New Covenant to replace the Old, as Jesus had not yet died for the woman's sins.

God the Father did not have a personality change with the coming of the New Covenant - he is eternally good.

From the Message Bible (John 8:3):

The Woman caught in adultery

 The religion scholars and Pharisees led in a woman who had been caught in an act of adultery. They stood her in plain sight of everyone and said,

 "Teacher, this woman was caught red-handed in the act of adultery. Moses, in the Law, gives orders to stone such persons. What do you say?"

They were trying to trap him into saying something incriminating so they could bring charges against him. Jesus bent down and wrote with his finger in the dirt.

They kept at him, badgering him. He straightened up and said, "The sinless one among you, go first: Throw the stone."

Bending down again, he wrote some more in the dirt.

Hearing that, they walked away, one after another, beginning with the oldest. The woman was left alone.

Jesus stood up and spoke to her. "Woman, where are they? Does no one condemn you?"

"No one, Master." "Neither do I," said Jesus. "Go on your way. From now on, don't sin."