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.
Fake Difficulty: Whilst this may well be one of the hardest AC games in general, this is only worsened by the dropping frame rates, awkward PSP controls compared to those of consoles and some ship enemies have invisible hitboxes!
Moral Event Horizon: The Hamlet unit's use of a biochemical agent to attack Santa Elva makes it quite difficult to sympathise with Leasath's military. So does the Gleipnir captain attempting to use his Shock Cannon to blow up Santa Elva just to spite Gryphus One.
That One Level: 7C, Time Limit! You are tasked with dumping antidote bombs on nerve gas outlets that have been released on Santa Elva by the Hamlet terrorist unit of Leasath, just like Mission 12 of Ace Combat 5; however, the antidote bombs in ACX are VERY unstable, meaning too much G-force from your plane (such as accelerating too quickly or doing really sharp turns) will detonate them and kill you, making your mobility and speed (combined with the aforementioned time limit to clear the toxic gas before it kills any civilians which fails the mission) very limited. Hard enough? No?! Here, have some enemy planes not only hunting you down whilst you are trying to clear the gas, but make fun of your flying because it sucks whilst you try not to get killed by your bombs! Thankfully, after getting rid of all the gas, your bombs automatically empty out, allowing you to slaughter the mouthy enemy pilots.