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.
YMMV: Magna Carta 2
Game Breaker: The DLC weapons are the strongest weapons in the game, and can be used almost immediately.
What an Idiot: Melissa. After the Northern Forces raze her homeland and nearly kill her, she somehow believes everything they tell her about their reasons and joins them. When she finds out that they've been lying to her, she's polite enough to hand her notice into Claire first. Claire warns her that Bad Things will happen if she switches sides, pointing out Melissa's mysterious chest pains and how she miraculously became good as new after almost being killed by Elgar. Melissa ignores this, joins your party for about ten minutes, dismisses her chest pains as "nothing" (when in the presence of the one friendly character with the experience to identify and fix the problem), and then is promptly turned into a Sentinel and forced to be put down.
Raud. While he has several moments showing that he is a good tactican, his status as "adviser" leaves much to be desired. Even though he finds out that Alex is in cahoots with Schuenzeit and is manipulating the course of the war, he waits until after the next battle to say anything to Zephie, by which time Alex and Schuenzeit have skipped town. This is despite the fact that he is present at said battle and doesn't even hint that anything is amiss when you talk to him. Then he decides to believe what the villains say and turns on Zephie.
Schuenzeit has a particularly stupid moment before the game even starts. Why was he so surprised that Juto fought so hard to save Zephie when he himself implanted Juto with the command that "you must not allow the princess to be killed", even going so far to add the condition, "this order supersedes all others"? You could argue that this single act is the root cause of everything that goes wrong with his plans.