The most disgusting invention of the 20th century is obvious. It is the invention and proliferation of nuclear weapons. No other innovation can claim to touch every human being's life. The A- and H-bombs are the only thing in the whole world that everyone can come in contact with, and they are designed to destroy us.
So who to burden with this? Oppenheimer is the obvious choice. Einstein would make sense as well. But what about Sakharov?
Andrei Sakharov was a courageous Oppenheimer. He worked on the Soviet Union's Atomic and Hydrogen bombs. He undoubtedly helped create the arms race, and the Tsar Bomba: the largest nuclear device ever detonated, with a 50 megaton payload. Just after these developments he turned to the positive forces of nuclear power, trying to make nuclear reactors and facilities safer.
Further, we have Sakharov to thank in large part for the Partial Test Ban which ensured that neither power used nuclear weapons underwater, or in space. Eventually, under Khrushchev, he began to vocally complain about nuclear weapons and their impact. In the process he became one of the most important critics of the USSR from within.
Different people in the U.S. mirror bits of Sakharov's work, Linus Pauling for example. But it takes more to stand up to a Premier than a Kennedy. Sakharov left the world a more dangerous place by being instrumental in the Soviet hydrogen bomb particularly, but he immediately began to campaign against what he knew had been a fatal error.
His disarmament and pro-democracy legacy continue, as does his hope that nuclear power may be reigned in for humanity's benefit. Of all persons involved in creating these terror-instilling devices, he is remarkable as the least offensive, even being positive role for the future of their use.