Ashoka the Great (304 BC – 232 BC)
Ashoka may be the strangest among all ancient generals on this list, as not only was he a great military leader, but he is the only one who later in his life simple refused to wage wars. He was the Indian emperor of the Mauryan Dynasty. During his first 8 years of rule, he was bloodthirsty and he expanded his empire to cover land from Assam to Afghanistan, with only the most southern tip of Indian subcontinent out of his rule. This culminated with the conquest of Kalinga, which led to the death of 100 thousand soldiers and civilians. Afterwards, he felt regret, so he decided to make his rule more peaceful, avoiding any wars. That way he remained undefeated until his death.