General Fan La was a high-ranking official in the Chinese People's Liberation Army during the 1970's, allying himself and his troops with Leviathan in order to further both their mission and his own goals of ensuring the People's Republic of China would be the leading superpower in the world.
The S.H.I.E.L.D. board of directors soon received a distress call from the Lhasa principality when General Fan attacked the province using reverse-engineered Leviathan-HYDRA tech, and sent their best field agents, led by Colonel Nick Fury and Hank Pym the Ant-Man, to deal with the threat. Hank used the Pym Particles in reverse to become a Giant-Man and smash down General Fan's base, but he was attacked in turn and knocked into an electronically-charged cage designed to contain him. Fury, in the meantime, was able to sneak into the General's HQ and used special hacking equipment to disable the HYDRA weaponry and allow Hank to break free from his cage. Hank then directed the SHIELD field agents to protect Lhasa and its civilians while he repeatedly used the Pym Particles to shrink and grow at will and take out General Fan's terrorist soldiers and remaining tanks. With his plans foiled, General Fan tried to escape, but Giant-Man pounded his fist to the ground to create an explosive earthquake and knock the Leviathan officer out. Fan was soon taken into custody by SHIELD at Taiwan, where he was interrogated about the whereabouts of Leviathan and how he was able to acquire the HYDRA technology, but he refused to comply and has since remained imprisoned in the base to this day.
(To be further edited with some clarification by Poolemax)