Actors who never met their full potential?

R. Lee Ermey - Although mostly typecast in military roles after his brilliant breakout in Full Metal Jacket, Ermey was actually a great actor with excellent comedic timing and very diversified range of emotions. I'm not sure if it was his fault, his agent's fault, or people in Hollywood only offering small cameo roles as angry military sergeants, but in an alternate universe, Ermey is being celebrated as a legendary actor beyond just Gunnery Sgt Hartman. David Fincher was very close to casting him as the villain in both Se7en and Zodiac because he was blown away by his audition tape but ultimately didn't due to the fear that people would only see Ermey as "that army guy". Such a shame.

Bill Paxton - I think people like Paxton, but his performance in One False Move is jaw-droppingly good. Gene Siskel called it the best performance of the year, and this was before Paxton was a known actor. He was also excellent in A Simple Plan and of course TV's Big Love, but other than some hits in the 90's that didn't really utilize his acting chops (ahem, Twister), Paxton never really broke out beside small co-starring roles. I really think eventually would've received an Oscar nom at some point had he not died so suddenly.