The list is of bad performances so DiCaprio doesn't qualify.

There's no evidence that Nell was intellectually disabled beyond her lack of language.

The character he played in "A Simple Plan" was even more pitiful than Karl.

I loved "The Ringer" … very sweet movie, but Christy Brown in "My Left Foot" is not at all mentally challenged, just physically disabled from CP.

Great movie, great story, great performance. I loved everything about it.