He’s the kind of guy who never does something halfway, so he must have a magnificent plan to steal the 3106 carat diamond.
Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means steal, so the verb vocab version is to steal.
What are you going to steal? How about a noose (ぬす)? Wait, why are you stealing a noose? That sounds like trouble to me...