These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Tear Jerker: Many. But Felicia biting it is the worst. She didn't die but ended up brainwashed by the Big Bad and doesn't remember Felix.
The Woobie: Ruby, especially post time skip when she must deal with Fenix going berserk and taking it out on her. She still stays by his side because she knows he's a Woobie too.
Jerkass Woobie: Fenix, post-time skip. He becomes a Jerkass and is basically a domestic abuser for Ruby. But he thought that Felicia died, it's implied her Regis Knights died, and he's had to cope with the Devilshu curse. Then when he finds out that Felicia is still alive, he learns that she's been brainwashed into being Diha Shion's lapdog with no memory of her past life.