Dr. Yi Suchong was a leading medical researcher in the undersea city of Rapture, studying ADAM, researching the creation of plasmids, and experimenting in mental conditioning. Always referring himself in third person, Suchong was an opportunist, using even tragic events to his own benefit and conforming perfectly to Rapture's hedonistic, morality-free society. His years before Rapture are clouded, but he mentions in one of his audio diaries that he was one of the few (if not the only) survivors of a Japanese assault on his home city, which implies that his survival was in part due to a position in the opium trade.
Suchong was responsible for the mental condition of Little Sisters and their protectors, the Big Daddies. He gave the Sisters the "need" to constantly gather ADAM from corpses around the city and gave Big Daddies the "need" to protect them at all costs. However, the latter ultimately lead to him being killed. One day, a Little Sister was interrupting him while he was recording an audio log. Frustrated because he believed he had again failed to implant the "protection" code into the Big Daddies, he struck one of the girls. This instantly activated the protection bond in the nearby Big Daddy, the same protection bond that he believed he had failed to successfully imprint. The Big Daddy approached and impaled him, leaving the drill stuck in his torso. His body can be found in his office in the first BioShock.
In BioShock Infinite and its expansion, Burial at Sea, it is revealed that Suchong had discovered the existence of parallel universes and had been collaborating with Columbia entrepreneur Jeremiah Fink through cross-dimension channels. The two exchanged research on imprinting and Vigors/Plasmids.
In Burial at Sea: Episode 2, Elizabeth witnesses the death of Suchong at the hands of the Big Daddy, one that she had helped heal just prior. She retrieves the activation phrase from Suchong's office for Atlas to use in controlling Jack, the protagonist of the first game.
Following his demise, Gilbert Alexander took over his work.