Ricardo Montalban did not receive an Oscar nomination for portraying Khan Noonien Singh in Star Trek II: The Wrath of Khan.
Ricardo Montalban is the only actor to play the main villain of Star Trek film after having previously played the role in the television series. Khan appeared in the original series as a superhuman from Earth's past bent on some new domination before he is stopped by Captain Kirk (William Shatner), through mostly the use of a particularly plastic looking pipe, and marooned on an apparently suitable planet. That's shown to not be the case early in the film when Khan is stumbled upon by another ship's Captain and one of Kirk's former men. Montalban's initial appearance, where he removes an elaborate mask, is so built up that technically Montalban has a great deal to live up to right from the start. Well Montalban lives up to this. On the surface at least Montalban brings back similar elements from his performance in the original episode. Montalban in the role is very cleverly menacing as he still has a very naturally charming manner in terms of his voice and whole manner. He's still kinda a perfect gentleman, but he also happens to be a very intimidating one.
Montalban though of course also shows a great deal of change in Khan expressing what is that Khan and his people suffered after being left to fend for themselves by Captain Kirk. From his first scene Montalban establishes the desire in Khan for revenge against Kirk quite effectively. Although he still keeps his refined demeanor for the most part Montalban conveys the searing hatred in Khan as he asks about Kirk and that bit of venom in his voice when hearing he is now an admiral is perfection. Montalban though does well though not to show this as just Khan being an evil bad guy, who did not like that he was defeated in the past sort of anger though. Montalban makes it much stronger than that, something far more personal. One of my favorite moments in his performance is when he mentions the death count caused by the only remaining creature on the planet a parasitic worm. When Khan says that one of the casualties was his wife Montalban is excellent as he expresses that the strongest emotions in Khan are in that breath. Montalban shows that he's not after Kirk simply because he beat him, but because he truly wronged him.
Khan then proceeds to become almost in a different movie in that we only ever see him outside of scenes with Kirk and crew except for over the communication screen. That's kinda enough just for as Montalban is concerned, although I do think the film would have benefited if Khan had been a more active and physical presence throughout the film. Anyway though Khan becomes technically a particularly self-indulgent revenge seeker purposefully seeming to want to be Captain Ahab. This might have come off as a bit much if it were not for Montalban's brilliance in the role. Every single one of Montalban's dramatic deliveries of Khan's soliloquies is pretty amazing to be sure. He makes each one a little gem of its own as he brings so much conviction into every word. It does not seem to be a man who's just kinda acting out his literary knowledge for fun, no Montalban portrays it with an absolute determination that Khan sees himself as such a character and sees his quest against Kirk as something of far greater importance that technically it really is. Montalban technically does show it to be ramblings of an obsessed madness while doing it with such wonderful style.
Montalban has just enough fun in the role because he basically channels into the "fun" Khan is having while he's taking his vengeance against Kirk. Montalban suggests Khan as completely relishing every moment in which he sees Kirk suffers, and believes that he will find his satisfaction at last. Montalban in turn makes the various setbacks rather satisfying for the audience as he shows such a striking disbelief and fear of losing what he's waited so long for whenever Kirk ends up tricking Khan one way or another. Although I do believe the film could have utilized Khan more in the film Montalban does succeed in making his presence always a factor in the film even when he's off screen by making such an impact when he's onscreen. Montalban though does create a great little personal story for Khan, which again don't feel connects enough with Kirk's story as one would think that it should or at least could. Montalban though is terrific though as his performance here is what turned Khan into probably the most memorable villain from the Star Trek series and one of its most iconic characters. Also just on all its own Montalban gives a fairly remarkable portrait of a man consumed by his obsession.