Here we have George III or George William Frederick, famous for losing the American colonies and his mind, George ruled the Kingdom of Great Britain and Ireland, as well as Prince-Elector of Hanover from 1760 to 1820, being the longest reining male monarch in English history. He also ruled throughout The Napoleonic Wars and expanded holdings in India, his greatest achievement I think is being a big voice in abolishing slavery in Britain and the banning of the transatlantic slave trade.
George III also had a mental illness that is still somewhat unknown, the most likely cause being bipolar disorder or portfolio.
I've always liked George, even though I'm American, I like to think he did his best despite his mental health.