Re: what is that one amazing performance from an otherwise mediocre actor?
 

Tyler Perry in Gone Girl

Re: what is that one amazing performance from an otherwise mediocre actor?
 

Sylvester Stallone in Cop Land

Sure, he was good in Rocky, but he wrote the part for himself, so he could tailor it to his range and abilities.

Re: what is that one amazing performance from an otherwise mediocre actor?
 

By that same token, several actors write parts for themselves and fail spectacularly.

Re: what is that one amazing performance from an otherwise mediocre actor?
 

And I would argue that's a mark of being a terrible actor, while this thread is about mediocre ones... ;)

Re: what is that one amazing performance from an otherwise mediocre actor?
 

I came here to post this. Calling Marlon Wayans "mediocre" is a compliment yet he was great in Requiem for a Dream. Darren Aronofsky is great at getting the best out of his actors.

Re: what is that one amazing performance from an otherwise mediocre actor?
 

Shelley Duvall in The Shining, shame about her mental illness

Re: what is that one amazing performance from an otherwise mediocre actor?
 

If Alec Baldwin can be considered a "mediocre" actor, I'd submit Blake in Glengary Glenn Ross.

Re: what is that one amazing performance from an otherwise mediocre actor?
 

Hugh Jackman - The Fountain
Scarlett Johansson - Under the Skin

Re: what is that one amazing performance from an otherwise mediocre actor?
 

Her performance in this movie perplexes me. There are times in it that she really shines (pun intended), but then she also has a handful of dreadfully acted scenes. Her delivery of lines in the scene when she's talking over the radio makes me cringe every time.

Edited to add: My vote goes to Anna Paquin in The Piano.

Re: what is that one amazing performance from an otherwise mediocre actor?
 

Tom Cruise in Magnolia. While he has had other good performances, even in those it was a toned down version of cocky guy faces trouble, learns something and wins in the end. But Magnolia had me wondering "who is this guy and what has he done with Tome Cruise?".

Adam Sandler in Punch Drunk Love. I generally can't stand him, but he caught me by surprise in this one (Spanglish is another).

Re: what is that one amazing performance from an otherwise mediocre actor?
 

I thought he was just as good in Born on the Fourth of July, Eyes Wide Shut & Rain Man (IMO he was better than Dustin Hoffman).

Re: what is that one amazing performance from an otherwise mediocre actor?
 

Tom Cruise is amazing in Interview With the Vampire. Played totally against type.

Re: what is that one amazing performance from an otherwise mediocre actor?
 

Jennifer Lopez in Out Of Sight. When that movie came out I instantly became a huge fan. She seemed fantastic.

It was an immediate descent into mediocrity afterward.

Re: what is that one amazing performance from an otherwise mediocre actor?
 

Ryan O'Neal - Barry Lyndon

Re: what is that one amazing performance from an otherwise mediocre actor?
 

Ryan O'Neal was Da man in The Driver.