In the Old Testament God was big on punishment and smiting. Think Sodom and Gomorrah, the Flood and the plagues sent down on Egypt. God was one vengeful deity in those days. Cross him at your peril.
But when his only beloved son was tortured and murdered by crucifixion what did God do ? Absolutely nothing. If that isn't the mother of all 180's I don't know what is. What would Anna Nomaly have to say about this ?
No turn, God is perfect justice and perfect mercy.
You repent, you get mercy, you dont, you get Sodom boom. People in the new testament were smote dead by God too for lying to the apostles.
Also, from God's perspective, sending someone to the afterlife can be an act of mercy, the people of sodom kept injuring their souls by staying alive in sin, while dead they cant injure themselves anymore. Like taking a knife out of a kids hand. It only seems harsh from a material point of view.
Old testament is God for spiritual beginners, normally people respond better to justice than mercy, so He taught people little by little. As people advanced spiritually they were ready to see God as mercy (some still werent so they rejected Him).
Even today we see this, many who are beginners follow God's will to avoid punishment and hell. As they grow and know God better they start doing it out of love and the thought of sin becomes aberrant not because of fear of punishment but because of not wanting to disappoint a loving father who made us to be perfect.
That's a common line of thinking. However, a careful study of the bible shows a slightly different story. In the OT, He is very patient with mankind. He tells them over and over how they are doing wrong. After a certain amount of time with mankind not obeying, sometimes many generations, He finally has enough and brings the hammer down. It's like a king with an unruly population. Because He is loving and merciful He lets a LOT of stuff slide. When He finally has to fix it the hard way, you don't want to be there.
The OT takes place over a very long time. The NT is short. It's the story of Jesus and the ministry of Paul to the early churches. It's really hard to compare the two.