If he returns to the past before the events that led to Carthaginian victory and restores his original timeline by negating the assassinations and military upset that have led to the new alternative timeline, he would wipe out its billions of inhabitants when the course of human history reverts to his own.
If he returns to the past before the events that led to Carthaginian victory and restores his original timeline by eliminating the assassinations and military chaos that have created an alternative reality, he would eradicate its billions of inhabitants when human history returns to its original path.