Taishaku-ten

Taishakuten is the villain in the manga RG Veda. A strong-minded man and a fearsome warrior who gained the title of "thunder god". He is in love with Ashura-ō and "will do anything to get what I want." Therefore, Taishakuten made a deal with Ashura-ō: he could have the Ashura king, but had to fulfill his wish of preventing Ashura's son from becoming a God of Destruction. This leads to the painful act of him eating Ashura-ō later, as Ashura-ō said this is the only way for him to have strength to rebel against the Emperor. Taishakuten then successfully killed the Emperor and got the title himself, becoming a tyrant just to fulfill one wish of the man he loved. According to Taishakuten, living alone without your loved one is extremely painful, as he had always suffered being without Ashura-ō. (Source: Wikipedia)