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: Arc the Lad
Awesome Music: While not very well-known, the series' soundtracks have a few really good themes, like the boss theme of the Romalian generals, the anthem of the Academy in Arc 3, Arc 2's end credits theme (chances are you'd be weeping so much, you wouldn't hear it properly while you were playing) and, of course, the series' main theme.
Game Breaker: The Romancing Stones allow anyone who equips all four of them to use magic without spending MP. Find them and the protagonist can solo his way to the end credits.
There's also Choko, the insanely powerful optional character you can acquire in several of the games. In Arc 2, if you power her up in a sidequest she can pretty much single handily win the rest of the game, and it becomes even easier if you give her the Romancing Stone.
Moral Event Horizon: Seyra commits a genocide during the first scene of Arc 2, then we learn about the experiments done by Romalia to turn children into monsters used for warfare and to create mind control devices, then we see Gallarno forcing Elc to kill his childhood friend... and that's only the first fifth of the game: the Moral Event Horizon is crossed on a daily basis here.
Player Punch: Present in every game in the series, but in Arc 2 it is taken to a form of art. Between the constant crossing of the Moral Event Horizon and the fact that every single playable character is a Woobie (yes, even Choko), it almost seems like the story writers were trying to break a record (and probably succeeded).
First, when Elc has to kill Mariel, his first love interest, right below the playground where they played together as children. Even worse is the Hope Spot where she breaks free from her mind control, only for a bomb wired inside her to detonate and kill her anyway.
Then there is the fact that Arc finally found his father, after literally YEARS spent looking for him, going into exile while being framed as a terrorist, and he dies 4 minutes after that. Finding his father was the reason he started his quest.
Then you can add the utterly screwed up backstories of most playable characters, and finally the events before the last boss: the characters have destroyed bit by bit the Romalian War Machine, freed most if not all of their puppet states, and have conquered its capital. Cue the king of Romalia breaking the seal of the Big Bad: it turns out that the key of the final seal was that a human being had to willingly choose to free him. Cue the king snapping because his kingdom is collapsing under his feet and pushing the red button. The Big Bad then proceeds to kill the King of Romalia (no big deal), kills Arc's girlfriend (a big deal), and unleashes the apocalypse over the world. Then you see a scene of the cities explored by the heroes being flooded and burned down, while most of the world's population dies.
Not only were all the good deeds of Arc, Elc & co for nothing, but you are at the end of the game. No opportunity to fix anything, and if this was not enough, Arc commits a heroic sacrifice after the last battle.
The Dark One is the hardest boss in the entire game. He's so strong that, unless you have a powered up Choko in your party, you're going to have to level grind a ton if you want to even be able to scratch him. It's not recommended to take him on with a party below level 100. You can also expend 2-3 hours of real time constantly buffing Elc and Gruga over and over before taking a single swing each at him and then running back out of range to repeat the process until he dies.
That One Sidequest: Arc 1 contains one of the most ridiculous sidequest goals ever: win 1,000 Arena battles. The battles are easy, and by the time you've gotten even halfway to 1,000 wins, you'll have earned enough experience points to bring your entire team to the level cap several times over. The primary challenge involved in getting to 1,000 wins is simply being obsessed enough to keep fighting the same enemies, over and over again, for hour after hour, in spite of the sheer tedium involved in doing so. If you're actually insane enough to reach 1,000 wins, the Arena manager will reward you with a huge supply of the game's best accessories for you to take with you into the sequel, then tell you to turn off the console, go outside, and get a life!
Most of the jobs sidequests in Arc 2 are decent, but there are the three or four jobs that require you to head into the Banza mountains. Your be forced to tediously kill the same monster groups over and over again each time you re-enter the mountain.
Tough Act to Follow: Neither 3 or 4 is a bad game, but they had the misfortune of being set after Arc 2.