First of the Fallen

The Lord of Evil ladies and gentlemen

This character has interesting story about his creation. The First of the Fallen was intended to be the comic Hellblazer's version of the devil. However, it was revealed in Sandman (which is in the same universe) that Lucifer was the Devil. So, Hellblazer creator Garth Ennis established the First as another character. Despite this, he still managed to screw up continuity.
History
God created the First of the Fallen before life and the Heavens. The First was made to be God's conscience and confidant. However when First discovered God's mental state was worsening, God sent the First to Hell. The Second and Third of the Fallen were banished to Hell soon after. Assuming they had equal power, the First had them become the ruling trinity of Hell. However, Lucifer took over Hell, but later left. As such, the trio returned to power. However, this seems to contradict was established with Sandman (since, in that comic, Remiel and Duma were given control over Hell). John Constantine first met the First in Ireland. It turned John's friend, Brenden, sold his soul to the First of the Fallen. John tricked the First into drinking holy water, which caused him to puke blood and distracted him long enough to let Brenden's soul go to Heaven. The First tried to steal John's soul when he died so the First could torture him. However, Constantine made a Faustian deal with both the Second and Third. To avoid a war over John's soul, the trio was forced to bring John back to life. First became an enemy of Constantine and his friends. The First discovered the Third and Second weren't as strong as him. He killed both of them, but only to be seemingly killed by the succubus Ellie with a knife that made out of the Second and Third's remains. In reality, the First was reborn as a fisherman with the memories of his past. Despite this, he managed to regain his former position. However, he didn't get John's soul, but parts of it that Constantine discarded. The First still constantly fights John.
References:
http://www.comicvine.com/first-of-the-fallen/4005-27431/