This movie with Shawn Penn finding out his daughter was found dead. The agony and pain he showed as a Father loosing his child, he acted the part as if he had really had lost a child . It was like an arrow thru my hear. I know I lost a child.
Very difficult to pick just one since each era has its major actors. As well if you watch more than just Hollywood film you might have actors that have touched you in their portrayal of a character.
Hollywood of old - Cary Grant, Katherine Hepburn, Audrey Hepburn, Spencer Tracy, Brock Peters, Dorothy Dandridge, Lena Horne, Bette Davis, Joan Crawford.
Italian - Marcello Mastriani, Sophia Loren
Hindi Cinema of old - Raj Kapoor, Mahmood, Nargis, Sridevi (sadden by her passing), Dharmendra, Raj Kumar, Dilip Kumar, Rekha ...
Hindi Cinema more present-day and have proven the test of time - ShahRukh Khan, Amir Khan, Amitabh Bachchan, Anil Kapoor, Kajal, ...
This question and expected response to only being for many Main Stream Hollywood film - limits the field. There are excellent performers in so many other film genres around the world. Names that many of us have never heard. But if we were to sample their acting we' be sold.