Matewis: Age of Wonders1&2 If you progress far enough in the campaign then your hero essentially becomes too strong. As in, an army killing, city razing demi-god. It applies to, I think, about the latter third or so of the campaigns I played. It's unfortunate because it just sucks the fun right out of the game.
That was the main plus for me, really...
mqstout: "autobattle" in the games that have their largescale map and battlescale, such as Age of Wonders and Lords of the Realm. autobattle is always nightmarishly bad and ends with tons of casualties for you that you always feel pressure to play out each battle... But, if you do, good luck ever completing a game because you're going to spend all of your time in tactical mode.
I'd say that the main point of a TBS, not to mention a tactics game, is to be in the battles/tactical mode. If an "autobattle" mode exists it's normal for it to be much worse than if you'd be actually, well, playing, it's there just for those who're at a point where they just want to rush to the end and can afford it, in terms of losses, I guess.
MadalinStroe: The ending to a game should be easier, considering you've spent most of your playthrough getting more powerful. The end game shouldn't be the challenge, building up power should be the challenging part. Games are a power trip, and feeling overwhelmed/weakest after having spent 20-40-60 hours kills a game right at the end.
*nods* Though I guess I can take a nasty final boss, or whatever counts as such, as long as the difficulty up to that point gradually drops as the character(s) improve.
StingingVelvet: Basically I think endings should be more or less "normal gameplay" with greater narrative thrust, rather than trying to have "epic gameplay!" which more often that not is annoying rather than fun.
That's also a good idea. Some can get the "epic gameplay" right, or right enough, though... And, while still quite rare, those may be more than those who can get an epic narrative right, sadly.
toxicTom: After building your character with love and blood, sweat and tears - none of that matters when you reach the final boss, because this section is played by completely different rules. Worst game in this regard so far is Two Worlds 2 (base game), where I got so frustrated I actually cheated in the end just to see the final cut-scene.
Another offender is Risen but at least the final battle there is not very hard once you get the hang of it. Still it's really annoying when a game walks over all your player choices just like that and instead forces you to play in a certain way.
Gothic had the problem that the finale only worked as melee fighter or mage - archers were fucked. But that was simply an oversight (game design bug; over-compensated in Gothic 2 where archery was way to powerful against bosses).
True, but if the character development doesn't matter that much at the end, it may work. The examples you gave of TW2 and Risen may rather fit in there, with those final battles being more like puzzles, and about player rather than character skill. And Gothic had a pile of potions before the end, seem to remember it was pretty much just so archers will be able to make up for the deficiencies and still get though.
On topic:
Age of Wonders: That early timed scenario.
Arcanum: Black Mountain Clan Mines. Plus the fact that companions have a set starting level and if you don't want them to be left lower level you need to find them at the right time.
Bloodlines: The graveyard quest. If you don't have the right character build for it, not a chance, in a game that otherwise aims, and succeeds more than most, to allow for a variety of viable alternatives.
Divine Divinity: The wasteland. They did say they ran out of time for that part of the game, just threw it there, and it shows.
Evil Islands: The end. How's that for a case of what you did (or gathered) before then not mattering? Plus, crap narratively. I mean, who hadn't figured out the "surprise" by then?
Knights of the Old Republic 2: That almost-final part. Sort of similar to the Divine Divinity situation above, but possibly even worse.
Neverwinter Nights: Hordes of the Underdark: The battle against the Valsharess' army. Losing experience unless you're the one killing enemies, annoying.
Risen: Same as above, only worse, that big battle at the end of chapter 2, with the dozen or so allies and experience obtained only if you land the killing blow, and friendly fire and allies you accidentally hit ending up attacking you, or fighting each other if they accidentally hit each other.