In the slang that has developed around superhuman culture, "Ahab" (sometimes "Captain Ahab", but usually just "Ahab") is a derogatory term referring to any supervillain who obsessively pursues one particular hero above all others and beyond all possible reason. The best known "Ahab" in the Butlerverse was Simon "Simple Simon" Bieber, a villain who obsessively fought Knightblade during the late 60s and 70s. Simple Simon continued his war against the hero even after Knightblade publically retired.
A week after Knightblade's death from heart failure in 1982, police found Simple Simon's body in a hotel room in Chicago. The villain had hung himself, leaving a note that explained that, with his having "escaped his wrathful vengeance", the villain saw the world as no longer having a point.