I watched some of the scenes of destruction again last night.
I liked the scene were Cersei arrives in the tower to watch everything. She doesn't say anything, but the look in her eyes says that she's anticipating a great day. The idea that she might lose hasn't even entered her head. She's so confident.
And as they go back to her several times during the episode that look is gone, but she's in denial even as she watches everything collapse. The Golden Company-- wiped out in moments. The Iron Fleet-- in ruins. The ballistas-- destroyed. She remains desperately convinced that somehow something is going to go right for her, because it always has. When Qyburn finally convinces her that she's lost and they need to flee, we get this one little tear as she finally comprehends the totality of her defeat.
A lot of people wanted her to meet a violent end face-to-face at the hands of one of her enemies, but I think being crushed to death as her own castle collapsed on top of her was really a perfect ending for her. Really, she was killed by her own over confidence more than anything else. Being crushed under her castle was a great metaphor for her hubris causing her downfall.
-k