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.
Anti-Climax Boss: Darksol in the first game - Despite being the Big Bad behind reviving Dark Dragon and the boss of the penultimate battle of the game, he is incredibly weak compared to your party at that point and his only special ability is no real danger to anybody.
Character Tiers: To list the examples would take ages. Teel;deer version: There's a buttload of differences per each game. Even worse is when there's Tiers within the own classes. (This is due to Loads and Loads of Characters, of course.)
Zylo. Even before you promote him, his attack is powerful. After promoting him, he will tear through entire armies of enemies.
The Sword Of Light and the Chaos Breaker. Not only are they ridiculously powerful swords, but using them can cast spells as well, giving Max an effective ranged attack. The Sword Of Darkness subverts this by being cursed and its effect being a Useless Useful Spell.
Goddamned Bats: Bat creatures, almost exclusively appearing in the earlier stages of the games, can avoid all obstacles and barriers, and have a good chance of putting a character to sleep with any attack. There is no way to cure Sleep, aside from waiting several rounds for it to randomly wear off.
Mary Sue: Arguably Narsha in Resurrection of Dark Dragon, a character who was not present in the original game. She is Ramladu's daughter, who takes it upon herself to save Runefaust from her now-Brainwashed and Crazy father. She also uses a powerful weapon and owns some of the best healing spells in the game. Though in a game with relatively little character development (not surprising given Camelot's other popular series), it's hard to concretely pin her as such.
Particularly vexing to some is that she replaces Mae as Max's love interest in the remake, even stealing some of her lines at the end of the game (while Mae isn't even present during the scene). Narsha being compared to someone's shoehorned OC in a fan fic is almost valid.
Rescued from the Scrappy Heap: The archer class began as nearly useless early on but once promotion is gained and advanced weapons go on sale, they become perhaps the most effective way of battling robots and aerial enemies (especially dragons) found late in the game.
Scrappy Mechanic: Evasion rates. As you progress through the games, enemies become more and more agile to the point you can spend over ten turns waiting for that lucky flush that will finally wound a gargoyle!
Seinfeld Is Unfunny: It can be hard to appreciate the seri robotic enemies and aerial mooks (particularly dragons) late in the game. Especially after having been spoiled by later games in the series (in particular Shining Force 3) and sequel Fire Emblem games and more in-depth Turn-Based Strategy games. Shining Force had several clichés for the day; but right now it looks like a Category 5 Cliché Storm.
The first game also has plenty of balance issues, too. The remake also received some criticisms for many tropes it helped create alongside Fire Emblem.
Also, after playing Shining Force CD and Shining Force II, it can be hard to go back to playing the first one again.
Tear Jerker: Kane's death in the first Shining Force game.
Marionette in particular, who is also an Early Bird Boss - he has infinite MP and can cast Freeze Lv. 3 in a huge radius (which is basically an One-Hit Kill for one to five of your units on this point of the game), and his health is always regenerating, all of which makes him insanely hard to defeat even for a skilled Tactical-RPG player. The Power Ring can alleviate this a lot though.