Melissa McCarthy
The rest of the cast in this were great. I love Cathy Bates and Susan Sarandon. Both played their characters naturally and let the humor of the situation and dialogue work.
Melissa McCarthy needed toning down by the third act. Loud and boisterous was her character through 95% of the movie. When she and Mark Duplas were talking, she was awesome. But then they let her go over the top in the next scene. She can handle humor and drama. But, it doesn't work when they contrast too much.