There is nothing more dastardly than killing your king. No matter how much you might want to (see: King Joffrey) it is taboo. However, the characters are on this list are notorious for taking that extra step toward regicide.
To kill a king is one thing, but when he’s also your own father…ouch. In the classic tale of King Arthur and his Knights of the Round Table, Mordred is the illegitimate son of the King. Resentful and bitter over his position, Mordred betrays Arthur and mortally wounds him in battle. Thus, the reign of Camelot ends and Britain is forever divided. Good job Mordred! *sarcasm*
When the title of the series is The Kingkiller Chronicle, one would assume that well, a King is killed. Here is the catch: we don’t know which King because the series has not ended yet! So far, we know that Kvothe, a talented orphan musician will one day kill the king. Why or how is still a mystery. All we be revealed in the final book, Doors of Stone.
Not all King Killers are amoral. Take Jaime Lannister of Game of Thrones for example. Handsome, brave and a skilled knight, Jaime is the chosen bodyguard for the Mad King. When said Mad King decides to torch the whole Kingdom, Jaime betrays his role as protector of the King to save the realm. This shame will follow him for the rest of his life as well as the title, Kingslayer.
And finally, sometimes one must kill the king to become a king — a la William Shakespeares’ Macbeth. This tragedy follows the “honorable” Scottish General, Macbeth, who (spoiler) kills his friend to become King of Scotland. Witchcraft, madness and some creepy trees result in more bloodshed and death for poor Macbeth.