Henry VIII

In addition to subjugating Ireland, Henry VIII was such a character, I just had to list some of his accomplishments in his 38-year reign:

• His first wife, Catherine of Aragorn, was actually the widow of his eldest brother. She was 23; Henry was 17. They married just two weeks before Henry's coronation.
• He was an accomplished musician, author, and poet, an avid gambler, and excelled at sports, including real tennis.
• In 1513, Henry invaded France. His brother-in-law, James IV of Scotland, took advantage and invaded England, but was defeated and killed.
• In 1521, Henry brutally suppressed the European Reformation, but by 1534 he had created his own English Reformation, declaring himself head of the Church of England.  (For the first time, Mass was in English instead of Latin; the Catholic church would not follow suit for another 400 years.)
• As part of the Reformation, Henry dissolved the monasteries and seized their property--one-fifth of the land in England. He redistributed their holdings to new hands, creating a "landed gentry" beholden to him.
• He expanded the Royal Navy from 5 to 53 ships, which served no practical purpose at all. (Britain was not a seafaring nation at the time.) However, these would prove decisive under Elizabeth I against the Spanish Armada.
• Henry also built 43 palaces. Monarchs at that time had to fund all the expenses of government out of their own income, usually from rent on the Crown lands. Despite inheriting a fortune (£375 million by today's standards), seizing the monasteries (which provided an additional £36 million per year), and devaluing the coinage twice, he still had to ask Parliament for additional money, and died in debt.
• Although Edward I had conquered Wales 300 years earlier, Henry oversaw the legal union of England and Wales. (Wales was initially set to become part of Britain, but has retained its statehood.)
• He had six wives, two of whom were beheaded. ("Divorced, beheaded, died, divorced, beheaded, survived") During his reign, an estimated 72,000 people were executed. The "head roll" included one cardinal, twenty peers, four leading public servants, and six of the king's close attendants and friends, plus various heads of monasteries.
• All three of his surviving, legitimate children ascended the throne: Edward VI (by Jane Seymour) succeeded Henry at age 9; he died at 16. Mary I (by Catherine of Aragorn) restored Catholicism but died only 5 years later. Queen Elizabeth I (by Anne Boleyn) then restored the Anglican church, and ruled for 44 years. None of them had any issue, and when Elizabeth died James VI of Scotland (and great-grandson of James IV who had invaded England) claimed the throne..

His legacy, ironically, had nothing to do with his intentions. His break from the Catholic church was a short-term tactic to secure a male heir, but the Tudor dynasty ended with his daughter Elizabeth. His expansion of the Royal Navy did not lead to England becoming a seafaring nation; instead, Spain learned several important lessons (such as using cannons instead of archers and ramming) which assured them supremacy on the high seas for the next 200 years. And his reliance on Parliament for money changed the dynamics of English politics which would, in 100 years, lead to a civil war and the overthrow of the monarchy. Beat that, Obama.