Quinn and Gideon's death. She's just so shaken and manic and terrified.
Fitz getting shot. The whole episode.
Mellie's intense, sincere apology to Olivia after she catches Fitz basically drunkeningly feeling her up in an elevator. There's no plea to keep quiet or accusations of seduction—Mellie seems to really, truly feel bad for Olivia. Doubles as unintentional guilt slinging.
Several of the scenes involving Abby and/or David in Nobody Likes Babies, but the one where David charges in and accuses Abby of stealing an important piece of his evidence, his voice cracking as he says he trusted her because she said she loved him takes the cake. Especially when she insists she does, and he refuses to let her touch him.
Fitz: Did I do this to you? Or have you always been like this? Because if it was me, I'm sorry. I'm sorry.
In 3.03, when Olivia learns Huck is still trapped by his training, she comes home and goes off on Ballard, trying to find out why he's there. Her father and the president ring, but she throws both phones to the ground. The whole episode seemed designed to break her, and it works.
"Big Jerry," Fitz's dad, rapes Mellie. There's nothing to really add to that.