This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / The Emiya Clan
In Innocence Lost, Aleksi's servant is Vlad III/Dracula who retains a couple thousand years worth of memories from his immortal self, including those from the events in Hellsing and Angel Notes. He has to experience the dream cycle of all of these.
During Paradox Sun, Reiko is initially thought to be a Valkyria and is put under the jurisdiction of Clementia Forster who tortured and experimented on her for days to the point where Reiko mentally broke and attempted suicide.