監 oversee

Genghis KHAN used his one rifle to oversee the vassal's filling of the plate.

director ★★☆☆☆
監 (oversee) + 督 (supervisor) = 監督 (director)

movie director/ construction foreman / coach.

to supervise ☆☆☆☆☆
監 (oversee) + 視 (peer at) = 監視 (to supervise)

to supervise, or watch over a project. Also means, to guard bad people - guards at a prison, a teacher who watches students at test time to keep them from cheating. (BOOBOO: don't mix this with 警備 (けいび), which is someone who is guarding or protecting good people or things).