King James the IV (I think, maybe the II)
actually it was King James VI (of Scotland that is) who was also (and who is usually known as) James I (of England, although they usually don't mention that, choosing to think of Scotland as some sort of province of England perhaps).
He is known quite rightly as the traitor king in Scotland and was directly responsible for the legal, royal and governmental pursuit, prosecution and execution of many "witches". He is also the one responsible for commissioning the King James Bible, the first ever English translation of the Bible (up till now it was thought by the Roman Catholics that the Word should only be read in Latin, whilst the Greek Orthodox Church maintained that it should be read in Greek only), complete with appaling mistranslations such as "thou shalt not suffer a witch to live" (the original Hebrew translates directly as "poisoner")
And another thing, James VI was the reason why the play Macbeth shows Macbeth to be a tortured weak and ultimately selfish and bad ruler, when the historical Macbeth was by accounts quite a good king. Macbeth was from a different royal line from James VI however and so Shakespeare felt that Macbeth had to be portrayed in a poor light so the king wouldn't be pissed off that a rival family was being shown to be more virtuous than him (which wouldn't take much doing in my opinion).
Edit: and the same sort of thing for Richard III of England actually.