In The Patriot:
The movie character of General Charles O'Hara is based on the real-life Brigadier General Charles O'Hara. Just as in the movie, General O'Hara served as General Cornwallis' second-in-command in the South in the Carolinas and Virginia in 1780-81. However, he was still in the north until at least October 1780, so he would not have been present at the Battle of Camden.
In the movie, General O'Hara was portrayed as pompous and ingratiating. In reality, he was popular with his men and because of his illegitimacy, he was down-to-earth. He liked to drink and gamble, which is not the characterization that the movie would lead one to believe. Of course, he gets little screen time to really develop his personality.