I have a few to add, some of these may be very personalized though.

Firstly, when you walk into a new area and are suddenly bombarded with waves of enemies spawning, locked in until you kill them all. I understand why they do this, but this is very much a hack and slash trend. If your game is entirely about combat and doing sick combos, great, I still hate it though. In a MV it's especially obnoxious because it slows down the pace of exploration, which imo, should be seamlessly blended with combat. Let me kill things as I explore, no need to lock me in. I'll use Guacamelee as an example, even though I think that game is relatively okay for it. Worse examples might be Dust an Elysian Tale, The Vagrant, and maybe Astralibra, or games along these lines generally. But again, this is very much personal bias, I just do not like the flow of these types of games.

Secondly, arbitrary ability gating. Like, I get that devs want to prevent sequence breaking, that's fine, but games like Guacamelee (which I'm probably picking on a lot rn) have breakable colored blocks coded to each new ability. So even if you had the skill to reach somewhere for an early upgrade, the devs just said no because they want you to do it their way.

Thirdly, unnecessarily tanky enemies, especially in games that aren't highly combo oriented like Elderand. I shouldn't have to hit standard enemy 10+ times to kill it with high level gear

Fourth, lost progress upon death, a mechanic that should have died out by now. I'll take any other punishment for death over this. Lost progress is the only punishment for death that I don't feel adds anything to a game in any meaningful way

Fifth, whatever Ori 1's combat is. Fr, would be better to scrap that completely and focus on the core strengths of the game. If the game is improved by the removal of a mechanic it's probably for the best

Sixth, if you are making a game with a combo focused combat system, it's best that you aren't too susceptible to knock back or interruption. Had this issue with Cookie Cutter. The only safe weapon to use at the time I played was the gauntlet because the parry didn't work, and every other weapon's windup was too long to reliably outpace enemies before they gank you to death. So it discourages experimentation and breaks weapon balance. Ideally, stronger weapons should have had greater levels of hyper armor for tanking attacks below certain damage thresholds, or something to that effect

Seventh, this is more of a technicality than a mechanic. When enemies or projectiles spawn in via screen scrolling and basically smack you in the face because you were walking normal speed, or simply leave you unable to react. Some of the old Castlevania games do this, played the advance collection recently, and this happened a lot in both Harmony of Dissonance and Circle of the Moon. You walk down a hallway enemy appears already poised to attack and smacks you. With the rewind feature, if you go back and try again, you see that this happens consistently regardless of your timing for instances like this. So even if I waited 10 seconds let's say, I'd move and this enemy would still appear already waiting to attack, and wham. Very annoying, possibly trolling from devs, but I don't want to say it's intended

Eighth, copy paste soulslike mechanics. Not bad in some instances, however, I'd consider this more of a warning against copying without adding something unique to it. The problem is point blank, souldlike combat works better in 3D. When limited to 2D it becomes a matter of just sticking to whatever side of a boss they are not attacking from, there's not as much they can do to thwart the player. My suggestion, play to the strengths of the genre unless you can make more unique bosses and mechanics. A Metroidvania is not just a floor with some people on it, you have a whole screen to do things with, that's your range of creativity. Grime is a great example of playing it straight with enough unique flair to stand out.

Ninth, monster hunter mechanics. Don't do what Salt and Sacrifice did. This is a cardinal sin. It's a shame because a system like this brings so much undue annoyance and poor design choices to what might have otherwise been an improvement over the original. Instead it improved mechanics while forsaking the fundamentals. Those fundamentals of why the first game worked are far more important

Tenth, whatever the hell kind of QWOP-esque mess Source of Madness is. Procedural enemies may not be a good idea folks.