Only one correct answer.
It was of course Cain.
Cain killed his brother Able, at the time, the only other people on earth were their parents Adam & Eve.
What the fuck you lot being taught in school these days, or don't you bother going anymore.
Adam and Eve. Surviving son Cain. In order 'to be fruitful and multiply', I guess incest started eons ago.
I mean, where did humans #4, 5, 6 and 7 come from?
Gotta admit, the snake remark was clever.
after cain killed abel, God condemned him to be a wanderer, rejected in all places he went. how could he be rejected by many if there were no others to be rejected by? the bible said "cain knew his wife" in the land of Nod, "east of eden". his wife couldn't have been his mother because in Leveticus it says "the nakedness of your mother you shall not uncover". so there were more people on the earth, and Abel was not 25% of the population.
Actually; It was God himself who killed off 99.9% of the human family.
Remember the bit when Noah built the ark and only people to survive the deluge were Noah and his immediate family?
Kind of did a lot of smiting in his younger days. Sodom, Gomorrah, Philistines, Babylonians...
Sure glad he's chilled a bit since then, but isn't it always the same?
The older kids have to suffer much stricter disciple, ground rules, curfews etc (you know, smoten for Sodemy here, a pillar of salt there), but now the world goes to hell in a handbasket (drive by shootings, mass suicidal bombings, twin-towers, wars etc), and its like... "I know, but I'm watching "the East Enders" omnibus... now go and sort it out amongst yourself like good little children!"