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.
Similarly, the dark side ending for Jaden in Jedi Academy is actually preferred by a lot of fans. It's not that the light side ending is necessarily bad or that Jaden is an unliked character, but it just leaves the state of the galaxy in a more uncertain state without compromising the core characters of the series.
Kyle is a BadassGenre SavvyDeadpan Snarker who mows down trained soldiers by the hundreds single-handedly before beating the crap out of Boba Fett and a Kell dragon and becoming a Jedi. No-one is bothered by this, though, since he's the player character and it's fun to be a Canon Sue!
See also: God, which is just another name for Kyle.
Hazard Troopers without certain Force powers, AT-STs when lacking your own walker or fixed gun. The Heavy Repeater's concussion grenade launcher, the missile launcher, DEMP 2's and Force Lightning above level 1 also help if you have neither of the former two.
Also, the Reborn in Outcast, especially since the duels with them are pretty much a Luck-Based Mission. Shadowtroopers are even worse.
Rodian snipers in both Outcast and Academy, particularly on high difficulties when they can kill you in a few hits (with near-100% accuracy and able to fire multiple shots at a time, no less).
Jedi Knight includes the above mentioned AT-ST and also organic, dangerous enemies like the Kell Dragons, the Drugons and also the Trandoshan's guards, armed with concussion rifles.
In Mysteries of the Sith, basically every enemy on Dromund Kaas and in the Dark Force Temple are basically this. The fact that your weapons malfunction (except for the lightsaber) doesn't help.
Pretty much any enemy that uses melee attacks in Jedi Knight and Mysteries of the Sith since their attacks ignore your shields.
Once you max out Force Grip, you can use it to drop all but the most powerful of dark Jedi off a cliff or throw them into the air fast and high enough to kill them, allowing you to instantly kill the only enemies that stand a chance against you. Instantly, that is, once you do get it right, since Dark Jedi are very quick to use Push to escape.
In Jedi Outcast, the force speed power, which has the net effect of slowing the rest of the world down. With nothing but max-level force speed and a lightsaber, the final battle with Desann can be ended in less than ten seconds without him ever landing a blow.
Also Dark Rage in Jedi Academy; it makes you completely invincible, faster, and makes you cause more damage. At level one and two it's (very) slightly balanced by the fact it takes pretty much all your health to use (but it can't kill you in itself), at level 3 it only takes twenty health each use (force heal makes this easily recoverable between fights) and lasts more than long enough to destroy almost anything but the toughest of enemies (the only drawback being that there's a somewhat long delay before it can be recast if it does run out).
If you use the two sabers style, the game breaking move is ducking, slowly moving forward while crouching, while swinging your sabers wildly like a Cuisinart. It looks stupid, but it lets you defeat most if not all Dark Jedi enemies.
And in Academy, Rocket Stormtroopers (the ones with the jetpacks).
Don't forget those damned Gran and their thermal detonators. They appear throughout the series, but they're most annoying in Outcast, where they come in packs.
There are also the Force Grip Cultists, and their job seems specifically to be annoying as hell by force gripping you as much as they can. And if you break their grip by force pushing them they are likely to retaliate by spamming force push and pull at you.
Good Bad Bugs: In Academy, if you fall into lava in a certain level, you will quickly die, whether you have god mode active or not. If you use the "undying" cheat repeatedly (sets your HP to 999 every odd (first, third, etc.) time you use it), you will eventually notice that unlike in water, you don't make choking noises. In other words, you can breathe lava. It just melts you too fast to let you.
Memetic Badass: Kyle Katarn made the Kessel run in less than twelve parsecs. On foot.
Narm Charm: Most of the live-action cut scenes in Jedi Knight.
In the original Dark Forces, you've got the Dianogas that pop up out of sewage and roar in your face.
Stage One Dark Troopers. They look like walking metal skeletons with swords and are partially bulletproof. And Lordy, those things are fast!
Kell dragons. They're the size of tanks, they're practically unkillable (especially in Jedi Knight, where bullets magnetically deflect off their scales), and they sport gruesome Slasher Smiles.
Gran and Trandoshans, who serve as Elite Mooks in Dark Forces before assuming a more prominent role in the early levels of Jedi Knight. Trandoshans can easily kill you from as much as an eighth of a mile away with their plasma-loaded "concussion rifles", while Gran toss grenades down on you from high platforms or windows.
Gamorrean guards, at least after they Take A Level In Badass in Jedi Knight. Their evil piglike grunts are intimidating enough without those nasty battle-axes, which they can swing with deceptive speed.
Boc is probably the most unnerving of all of Jerec's followers in Jedi Knight. Not only does he wield two lightsabers at once, but he jumps around so frantically (and so high) while fighting you that it's easy to get caught from behind. That, and he's definitely The Hyena of Jerec's crew, creepily giggling and cackling nonstop until you finally slaughter him - and even then, he continues laughing until he finally chokes on his last breath.
Jedi Knight and Mysteries of the Sith have the Drugons, giant carnivorous fish which can kill you in one bite, can swim faster than you (if you're not using Force Speed), and may spot you from afar.
Jedi Academy has the Sand Burrowers on Blenjeel, which can swallow you whole if you're not careful. And that level is overpopulated with them. It doesn't help that the save file name for that level is "Danger".
The Rancors in both Mysteries of the Sith and Jedi Academy can be this.
The one in Mot S can not only kill you in two attacks, but it eats you alive when it defeats you, and you can only kill it with your lightsaber, which you won't have at first and must retrieve from a nearby vault after getting past the creature.
In Jedi Academy, on the Nar Kreeta mission, it's not as dangerous to deal with since you have ranged weapons that can affect it now, but it has a crapton of health, and it will just respawn if you kill it.
The Scrappy: Rosh: his personality and carelessness, among other things—such as the fact that the path to the dark side is to kill him—show that he may have been designed to intentionally invoke the trope. Runs into Alas, Poor Scrappy in the dark side ending, his death scene is oddly affecting.
Special Effect Failure: As a miraluka, Jerec donít have eyes, but we can clearly see his actorís eyes through his mask in the cut-scenes.
That One Boss: Desann at the end of Outcast (See The Computer Is a Cheating Bastard). Marka Ragnos at the end of Academy is also an insane fight if you don't have Force Absorb, due to his tendency to spam Level 3 Force Drain and Force Lightning, and his ability to heal himself to nearly full health a total of 4 times.
Dark Forces had Jabba's ship, a.k.a. the one where you have to punch Kell Dragons to death before they eat you. Jedi Outcast's arbitrary stealth mission certainly counts, though any level prior to receiving the lightsaber could apply. Then there's the first part of Nar Shaddaa, the first level you play with your lightsaber, also from Jedi Outcast, in which ten Rodian snipers are all firing at you at the same time and each can kill you in one hit if they want to and they all have great aim. Plus, they're hard to find and shoot.
Ironically, the pre-lightsaber levels become the most fun part of the game if the lightsaber is acquired early with cheats.