A summary of Doomsday’s personality is:

He is a genetically engineered creature from ancient Krypton, who was repeatedly killed and resurrected until he became immune to any form of death. He is driven by a primal instinct to destroy all life, and has no empathy, compassion, or morality. He is extremely powerful, fast, and durable, and can regenerate from any injury. He also has sharp spikes on his body that can pierce even Superman’s skin. He is not very intelligent, but he is cunning and adaptive, and can learn from his enemies’ tactics. He has no allies, friends, or goals, except to cause as much death and destruction as possible. He is one of Superman’s most formidable and dangerous foes, and a threat to the entire universe.