Fighting, winning, ruling, and losing,
His strengths were winning wars by using all kinds of tactics and keeping roads safe and organizing great armies.
His weaknesses were with actually ruling the places he conquered. While the Mongols were great soldiers and warriors and fighters, great rulers they were not, and after a while, partly due to his allowance of all kinds of religions and cultures and things like that, people got resentful that someone with a different culture/religion than them was ruling them, or that they had a bad ruler, or both, and they rebelled.
His failures were the occasional cities/countries that defeated him, and the rebellions which he didn’t manage to quell.