Dr. Suchong
Dr. Yi Suchong, likely of Chinese descent, was a leading medical researcher in Rapture studying ADAM and its uses to create plasmids and alter brain function. Suchong was an opportunist using even tragic events such as war to his own benefit. He conformed perfectly to Rapture's capitalistic society and worked simply for the highest bidder.
His years before Rapture are clouded, but he mentiones 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 further lends credibility to the idea that he is Chinese.
First employed by Frank Fontaine, Suchong was directly involved in creating the Enrage and Telekinesis plasmids. While Dr. Tenenbaum was responsible for the Little Sisters' physical ability to process ADAM from the dead, Suchong was responsible for the mental conditioning that gave them the need to "gather" the substance from corpses. Suchong realized that, though they were invulnerable to harm, they still only possessed the strength of small children and needed to be protected. He was instrumental in the creation of the Big Daddies and their mental imprinting that forced them to guard the Little Sisters.
During this time, Suchong was involved in Fontaine's project to create an "ace in the hole" weapon, namely, Jack. Suchong monitored Jack's rapid aging and implanted him with at least two mind control triggers: "Would you kindly..." which causes Jack to obey unquestioningly and "Code Yellow" which can ultimately stop Jack's heart. Suchong developed an antidote, Lot 192, to this mental conditioning.
After Frank Fontaine's death, Suchong was employed by Andrew Ryan where he continued his work on Big Daddies. Suchong's skill with implanting the Big Daddy's protection instinct led to his demise. During a moment of frustration, he slapped a Little Sister and was killed by a Big Daddy. His corpse is found in his clinic in Apollo Square, still screwed to an examination table by the Big Daddy drill that killed him.