In the Flashpoint continuity of DC Comics, Neil Sinclair (a version of the superhero Apollo), also known as Subject Zero, is a featured antagonist. He is the product of a government super-soldier program, called Project Superman, that, in this continuity, was responsible for cultivating Kal-El's powers.
Lieutenant Neil Sinclair was a soldier and the first volunteer of the United States Government's top-secret Project Superman, a program to create super-soldiers in service to the government, as chosen by General Sam Lane. He became known as Subject Zero and is tested on many times over the years. He eventually became cold and callous in nature and developed superpowers he hid from those who tested on him.
Later on, Sinclair became insane and accidentally killed several soldiers he was supposed to cooperate with. He was deemed a failure and the project's main focus became Subject One - Kal-El (who landed directly in Metropolis in the Flashpoint continuity and was immediately seized by the government after he landed as a baby.)
Sinclair used his hidden ability of telepathy to communicate with Kal-El for many years as the two grew up in captivity. When Kal was a boy, he broke Sinclair out of his cell. However, instead of escaping, he targeted Sam Lane's daughter Lois Lane, blaming General Lane for betraying him for Kal. Kal stood up to Sinclair, though, developing an attraction to Lois instantaneously. In an effort to save his daughter from the monster, General Lane blasted Sinclair and himself into the Phantom Zone where the two, together, lived in sentient paralysis for years.
Sinclair and Lane were freed from the Phantom Zone when a group of heroes came to rescue Kal, unintentionally cutting the power source to the Phantom Zone holding device. Free, Sinclair immediately finished what he started by killing Lane. Then, he hunted down Kal and Lois Lane, wanting to continue his revenge against General Lane. In their fight, despite being the better skilled and higher-powered combatant, Sinclair. was killed when Kal punched him through the abdomen.