K'inich Janaab' Pakal, or Pacal the Great, as he is widely known, was one of the Mayan city state of Palenque's greatest kings, or ajaws. He was barely 12 years old when he ascended to the throne in 615 AD, due to the deaths of at least three, and possibly four, of Palenque's royals in quick succession. His claim was also, rarely, through his mother, x Sak K'uk'.
Palenque was in great turmoil when Pacal (meaning 'shield' in Mayan) ascended the throne, having been attacked and sacked by neighbouring Calakmul just four to five years previously. And the first youthful years of Pacal's reign at least seem to have been heavily influenced by his mother. Still, when he was old enough, Pacal began rebuilding the state, and reconstructing the capital city. He also gained heavy retribution on his enemies - beginning in 659, when, in response to another Calakmul attack five years previously, Pacal stormed Pomona (a Calakmul ally) and took away several of its leaders for sacrifice. More wars were waged during Pacal's monarchy, but the details of these are hazy.