What is meant by "the actor" (al-mumaththil) in the hadith: "The people who will suffer the most severe torment on the Day of Judgment are a man killed by a prophet or who killed a prophet, a misguided leader, and an actor (mumaththil) among the actors"?

The meaning of the first part of the hadith is clear. "Imam of misguidance" refers to someone who is a leader in misguidance, such as the callers to polytheism, immorality, and innovation, whom the hadith describes as: "Callers at the gates of Hell; whoever answers them, they will cast him into it." As for "al-mumaththilun," it refers to image-makers who create statues. The punishment for the image-maker was severe because images were worshipped instead of Allah, and because looking at them can be a source of temptation.