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: Last Exile
Canon Sue: Claus is very good at anything to do with Vanships, like piloting, navigating, and mechanics, wins everyone over with his personality, and every female of age is attracted to him (and at least one male.). Especially when he's placed in the cockpit with characters who have reasonable flaws like Lavie and Tatiana, Claus comes out looking a little too good. It's reasonably justified because he wasn't some hick farmboy that's an Instant Expert as soon as he gets in the cockpit, he'd already been flying dangerous missions for years, and the Back Story shows him darn near getting killed a couple times earning his wings. And daring airplane pilots have always been Mr. Fanservice. However, he is an Extreme Doormat, and every time he's in combat he only barely survives/ runs out of ammo.
Complete Monster: Warfare, torture, brainwashing, duels to the death, slavery, murder; Delphine commits them all with a pleased smile and with great glee.
Fridge Brilliance: In episode 10, Claus and Lavie are seemingly abandoned at their docking stations by their crew during a blackout after a particularly harrowing race. They can apparently get out once the lights turn on a couple hours later, but are stranded in the meanwhile. Now this may seem like a particularly mean spirited thing to do until you take into account that Claus and Lavie are both healthy young adults with a close relationship. Claus and Lavie share their cramped quarters with a young child on a ship that probably doesn't offer much privacy. The crew left them with a good chance to win the race. The crew possibly assumed that celebrations would be in order.
There's also the probability that the crew wanted to provide Claus and Lavie with Plausible Deniability if something went wrong with the underlying caper they were unknowingly serving as the distraction for. Worse come to worse they'd be left behind where they'd be safe with a working vanship.
Fridge Horror: Dio seems like just a creep until we see he's genuinely terrified of his sister. And then we meet his sister. Just what did she do to him?
Ho Yay: The engineer Gale admits to a crush on Claus, and Dio seems awfully fond of him, with all that glomping and whatnot. Of course, everybody loves Claus in this series. And who does Claus get that doughy-eyed look of love for? His vanship. There's also considerable subtext between Tatiana and her navigator.
And the aforementioned Ho Yay between Dio and Lucciola.
Heck, the other mechanics predict Gale is going to make a play for Claus the minute they set eyes on him, judging from the banter. But we're never shown Gale doing anything beyond bemoaning his fate from the sidelines, however.
Nightmare Fuel: Delphine blows Lucciola to tiny pieces, then laughs and twirls as his remains fall down like snowflakes.
Moral Event Horizon: Delphine crosses it when she brainwashes Dio.She makes him do very bad things.
Or even before that when she causes a ship delivering water to refugees to crash on top of them.
Subbing vs. Dubbing: The dubbed version is quite good; special notice goes to Dio's voice actor, Joshua Seth.