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.
Crowning Moment of Funny: Anything in the Seraphic Gate. The Silliness Switch in this game is taken Up to Eleven here; with characters frequently engaging in playful skits making fun of the fact that they're in a game, obscurely powerful hamsters, and loads of mythology gags such as how Hrist is complaining about not getting her own game.
Game Breaker - The Destiny Plume is essentially an "I Win" button when you use it, albeit with the cost of a character. But for each character you sacrifice, you get a special tactic for Wylfred, most of which give your team such an advantage that they have no excuse for losing anything other than the escort missions once you've gotten a few of them.
Tear Jerker - When you consider that on the B path, Natalia was killed by her own children without even a second glance...
Also, any death scene after you use the Plume counts. Expecially since it was YOU who decided to sacrifice them...
That One Level - Early enough in the game, when you'll have done at most only one sidequest, if you chose the Rebel path, you get the mission to save Natalia. Who is already on the guillotine, which can't be reached without walking all the way around the map and past the level's boss, has puny attack, and is constantly attacked by a soldier who is supported by a mage ready to heal him and finish off Natalia. The boss can... no, WILL kill any of your units in one hit (expecially if it is your first playthrough), and thanks to the Combination Attack and his mook's wide range, can obliterate your whole party in one turn if you get too close to him.
The Woobie - Rosea. She wanders from city to city in a demon-infested world to heal those in need. Because of her good deeds, the citizenry goes as far as to call her a "Saintess." Even though they grant her this title, she hides behind a mask to hide her past reputation with the magic court and her hatred for Lieselotte. What's worse, she's not only a victim of Lieselotte's manipulations, but Fauxnel's, as well.
Even worse, you only get her in the C path, which is the worst path in the game. Unless you choose Natalia/Earnest in Chapter 2, she is surrounded by the most unsavory, broken, unsympathetic people in the entire game. The only exception is Duwain. She is then forced to spend much of Chapter 5 traveling with a Prince that she clearly dislikes and considers "unforgiveable", but can't do anything about. In the end, she is forced to fight the Valkyrie alongside Wyl, who is responsible for her allies being killed by the Plume, in what looks to be the same place Lieselotte is killed. If she isn't rotting in Nifelheim, then unless she flees Artolia, she will be stuck in a war-ravaged country ruined by infighting. The cherry on all this is that Fauxnel is the archmagus, and if she found out the truth, doing anything to him would accomplish nothing. Much of this is actually optional, like shattering her by pluming Duwain in front of her, but the game makes it VERY easy for players to make her life a living hell. In fact, Rosea ends badly no matter what she does. The most merciful thing to do might be to plume her. That way, at least she gets to live on as Lenneth's einherjar.