The Qing dynasty was the last dynasty that governed China. It's rule ended in 1911-1912 after some rebellions and mistakes made by it. Sun Yat-sen played a very important role during this events, he was the first "professional" revolutionary in China, he supported and organized the rebelions. After the dynasty's fall, he was named "provisional president" of the Republic of China, those are the reasons he is known as the "Father of the nation".
B Sun Yat-sen was the leader who emerged strongest following the Qing dynasty as well as the strongest Chinese leader until 1911 when he became the president.