TWOK Khan was a perfectly credible and psychologically believable Ahab analogue, that's his plot and his arc (one so satisfying that they kept going back to it for later Trek films, never as convincingly IMO) and it's visibly driving every frame of the performance, besides being reflected in everything from his character design to his environment. A couple minutes of exposition from Khan and Chekhov is all it takes to establish firmly and then we're away. Far as I'm concerned that's pretty darned good villain design; he's not just designed to be a robotic interchangeable Badass but an actual character, a once-great man driven into the abyss of madness and folly, and it works.