The question title is deliberately vague because I don't want to spoil anything.
Every ceremony in The Handmaid's Tale is a rape scene, but the one suffered by Offred in S02E10, The Last Ceremony, is particularly hard on her.
Why that time?
And why does she show vulnerability rather than maintaining a stoic strength like before? Why does she struggle that time, when it doesn't look like she has done so before?