This is based on opinion. Please don't list it on a work's trope example list.
Tearjerker / Celestial Refresh
Kotone returning to her world to figure out that, due to her no longer acting as The Seal, Nyx was unleashed on the Earth and everyone on it was killed. It shook her so much that her Social Link with Junpei reversed and her one with Aigis was outright broken.
She had kept trying to put on a brave face ever since then but it clearly has been effecting her health, to the point where her frustration of being unable to summon Metatron due to her broken link with Aigis caused her to become enraged and reckless to the point where she forgot all tactics and completely forgot about helping Chie, which in turn almost got Chie killed.