Maegor

Lore accurate dirty lion XD
WIKI/BOOK INFORMATION:
"Maegor I Targaryen, also known as Maegor the Cruel, was the third Targaryen king to sit the Iron Throne. He was the son of King Aegon I Targaryen and his elder sister-wife, Queen Visenya Targaryen. He had an older half-brother, Aenys I Targaryen."
-Wiki

Maegor was always a cruel child, often enjoyed violence. His savagery from an early age helped him become a fierce warrior, quickly climbing the ranks in tourneys then eventually war. He had a quick temper, and was not one for mercy. This helped the Targaryen dynasty greatly when he stomped down the Faith Militant. It also caused great pain, when he challenged and eventually murdered his half-brother's son for the throne, and by doing so also introduced the first dragon on dragon battle seen in Westeros (Quicksilver, Aegon the Uncrowned vs Balerion, Maegor I).

He died by being impaled on the Iron Throne. The people speculate the Throne killed him as it saw his as unworthy, others say one of his wives killed him after all the torture he put them through. Either way, his reign of terror was over.