Easily the most memorable , and ironically, best loved villian, not only of Trek, but in cinema. The Wrath of KHAN is considered one of the finest SciFi movies of all time not just a great Trek. That was in a great deal due to Mr Montalban.
This is not to diminish his other work on and off screen.
Utmost respect, and farewell. May God keep you and watch over you. Rest in Peace, Mr Montalban.
You may find that having is not so pleasing a thing as wanting. This is not logical, but it is often true." Spock (Amok Time)