Greg Nightmare is a character in killer7. The US Secretary of Education, Nightmare is an obese, besuited man with tanned skin and short grey hair, and, according to both Kenjiro Matsuoka and the tapes left by Holbert, the true power behind the US Government. He was hanged in the Coburn Elementary School gymnasium, possibly by Benjamin Keane.
After Garcian confronts Matsuoka in the gym, Greg comes back to life (possibly as a Heaven Smile) and attempts to take out the killer7 with the Golden Gun; the Smiths must shoot him from side to side until his trousers fly off, revealing that his legs are an unusual bright red and his crotch is a bulbous glowing orb. The player must shoot at the crotch, occassionaly taking steps to avoid or counter Greg's pistol shots if necessary, until his grown brutally explodes and removes his lower body entirely.
On doing so, a cloud of vapourous gore emerges from Nightmare's torso, and 7 invincible Black Heaven Smiles spawn on the stage beneath. Greg drops the Golden Gun, but the weapon can only be collected by Garcian Smith; thus, Nightmare is invincible while the Black Smiles pick off each member of the Killer7 until only Garcian remains. Garcian can take the Golden Gun, and then the player can eliminate the last Black Smile and attack Nightmare's torso, blasting his chest open and killing him for good.
- The theme which plays during the first half of the fight with Nightmare plays between 0:53-2:17 on Election Plot. The boss theme can be found separate from the main Election Plot variations in the game's audio files labelled 009_Boss CHO_hps.