Which mongol emperor had the last abbasid caliph trampled to death?

The answer is Emperor Hulagu. He sent wanted the Caliph (Al-Musta'sim) to demanded him to surrender the Capital. He promised to continue a governance and security to the land. However, Caliph (Al-Musta'sim), did not agree to Hulagu's terms and demands. T he Caliph (Al Musta'sim) refused despite the weak military condition of his territory. Hulago made an embargo on Baghdad and soon entered the city and killed Abbasi caliph (Al-Musta'sim).