Out of his entire filmography spanning the past couple decades, Quentin Tarantino says the best character he's ever written is Hans Landa. Played by Christoph Waltz, Hans Landa is the main antagonist of Tarantino's film Inglorious Basterds. Waltz did end up winning a best supporting actor Oscar for the role and went from unknown German television star to worldwide A-list status.
“Landa is the best character I’ve ever written and maybe the best I ever will write. I didn’t realize [when I was first writing him] that he was a linguistic genius. He’s probably one of the only Nazis in history who could speak perfect Yiddish.”
While Tarantino can toot his own horn all he wants about the perfection of that character, I don't think it would've translated with any other actor than Waltz. What set Waltz apart was his ability to be a native German speaker with the ability to comprehend Tarantino's writing style that best translates to an English-speaking audience. That's a real testament to his acting ability. I ultimately agree with Tarantino's pick, although it wouldn't have been my first choice...who would you go with?