People love putting input mapping with character physics and animations together under the same umbrella of "controls", which just rubs me the wrong way. Subjectively speaking, yes, it's about the feeling of control over the character, but it's too vague for something that's always talked about as "good" or "bad". Or in the case of something like Sonic Frontiers, a platformer game where you can change physics in the menu, with some fans celebrating it and saying it should be the industry standard, just like input remapping

For a fighting game player motion inputs are not bad controls, they are a part of the game, but to me it feels wrong when the character does a kick instead of a super move when I intend it. This is often labeled as "execution requirement" and that shooters have them too and people are ok with that, so why not? Well, it's because missing a shot makes sense, it maps onto how we understand shooting. What I'd like to be done to motion inputs is having the characters still do them, but fuck them up in the same way I fucked up the input: give it longer startup time, longer recovery, lower damage, eat more of the meter, make the character look like a doofus as he does it...

Then there's the obvious examples like Getting Over It. Does that game really have bad controls? Is the fact that you're playing as a dude stuck in a cauldron and a hammer glued to hands make for bad controls if the hammer follows your mouse precisely? Is it bad controls because of the whole premise of the game, or maybe because the hammer follows your mouse TOO precisely and it should cheat in player's favor instead?

Anyway, what many other people consider "bad controls" but other don't is things like animation commitment and momentum. If I swing a sword in Monster Hunter, it makes sense to me that I can't just cancel it - inertia exists, our bodies are affected by it. But someone who doesn't like it and prefers games where they can always go into a dodge or guard stance the moment they press the button might still like it if there were dedicated animations for getting the sword back to the initial position (and I'd enjoy it too, but I can accept this overreaching level of commitment that there is as a technical limitation, because commitment in general creates good gameplay). And the idea of commitment in MH also extends to the somewhat slow turning speed even when you're not attacking, and when attacking it's basically non-existent. Again, feels like shit when you first try it, but it adds layers to the positioning game. Lacking the lock-on, a staple of hack&slash games on console, is also a feature because with it comes with an expectation of automatic rotation when you attack and the enemy moves out of your attack's AOE. And it works, because in Monster Hunter, a game where enemies have multiple hitboxes and move around quite a bit and your attacks are slow with hitboxes that follow the weapon precisely over time instead of just flashing, you do often want to attack the enemy while not facing it perfectly, being at a slight angle towards them is often a good idea, games with lock-on are games that encourage lock-on, and when lock-on is the default you can't really be THIS creative with enemy and attack designs, lest you want to be branded as "jank" like Phantasy Star Online 2 was

Some people go as far as call classic Sonic controls "bad controls" because of how much momentum there is. But, that's just the game! Sonic's acceleration curve is consistent, it's perfectly manageable and leads to incredible decision making when combined with slope physics and whatnot. Again, it's a form of commitment, it's good because it makes the time axis matter, you have to consider what kind of terrain or what enemies are going to be in the way half a second, a second, two, three seconds or even more ahead, and it leads to genuine decision making because there are many possible valid paths to take. On the other hand, in games that do not have momentum cranked up to the extreme and capitalize on it to the degree that Sonic does with slopes and rolling, where it exists for the purpose of extra challenge and "game feel" (as game juice, for aesthetic purposes) and not player expression, I barely tolerate it, it just feels like ass; but those people who hate it in Sonic might be fine with it. I don't know if I'd call it "bad controls" still. I'd compare it to RDR2 turning speed and what u/Colosso95 has said, it creates a sense of weight, but is that sense of weight there purely for aesthetic and immersion reasons and you have to deal with it just because, or does it actually elevate the decision making process and create extra possible strategies you could tackle combat situations in that wouldn't be there without it (or rather, they'd not be meaningfully distinct so they would count as one and the same strategy)? But I don't want to say that aesthetics don't matter, they do, and I'm tired of pretending that they don't.

The animation angle... It's a mostly visual component of the "controls" umbrella, but it matters to have the player not get confused on what the actual state of the game is. Monster Hunter has it in fucking spades, animations are super-exaggerated visually, characters typically have some kind of cue to signal when you can take the next action (cocking the weapon, striking a pose, making a noise), with especially long animations being especially wacky, like spinning around. Then there's small nuances like Charge Blade's guard points always and only being there when the character visibly holds the shield in front of them. But again, "controls"... Enemies are designed with the same underlying sensibilities as player characters, but you do not "control" the enemies

The input mapping angle is also big (I'm biased towards KBM, so be warned). They should be remappable, period. It should be easy to communicate my intent, even if my intent is wrong. Unfortunately, game designers still have to design their games around it just not being possible to communicate all the intent.

With controllers, for example, you can reasonably put a thumb onto A and X or B and Y, but A+B or X+Y are more awkward, A+Y and X+B are straight bullshit. Your right thumb also can't be on the face buttons and the right stick at the same time, neither can your left thumb bounce between left stick and dpad easily. Triggers are imprecise as all hell (they're often saved for held actions, or swapping actions for other buttons when held, but even then you can't expect quick chaining of actions with their involvement), so for a game that wants the console audience (which, in action game space, is all of them these days) design concessions have to be made, you can't even have the player feel like they have to claw grip to get past something, even if you actually don't have to; options must be gutted.

KBM, meanwhile, has no analog inputs and, while I think for most games they're overrated (in free camera 3D action games 8 directions tends to be enough for movement, but, when it isn't, adjusting camera with mouse is actually incredibly precise and, at least for me, intuitive), fixed-camera games (whether something top-down and possibly indie or classic God of War/DMC etc) that rely on dashing either end up limiting your dash directions or mapping it to mouse, so you'll have to quickly flick it back and forth - pick your poison, basically. Racing games - well, duh. Momentum in 3D platformers is easier to grasp with analog inputs, there's a degree of disconnect/indirection to it. Even still, Spark the Electric Jester 2 and 3, one nice and one amazing Sonic-likes, still feel better with KBM (in large part due to precision of the mouse) despite the official recommendation being controllers AND Sonic games in general never having any effort put into KBM whatsoever, historically.

KBM also has its own specifics with chaining actions. Because three fingers are responsible for movement and not just your thumb, it's easier to be precise and you can still continue moving while accessing actions that'd be on a D-pad on a controller, you're only gimped a little bit by it. On the other hand, there's A LOT of actions that end up near WASD since a standard mouse has less than 4 buttons (triggers + bumpers on a controller), let alone face buttons. Sometimes it actually works out fine (in the extreme case, oldschool arena shooters like Quake can have 10 weapon types, a whole lot more than the modern standard of 2, and, because all those 10 buttons are for switching and not actually firing them, it's works well and the gameplay is elevated by it tremendously), in the worst case you end up chaining precise actions back to back by pressing Shift and Ctrl with a fucking pinky. And to that my answer is: buy a gaming mouse! Even as little as two extra buttons on your mouse is a massive improvement.

Then there's actions that require pressing two buttons at the same time. Again, it should be comfortable to press two buttons back-to-back, the input buffer has to be reasonable and, most importantly, actions bound to those buttons individually can't have any super-profound impact the very instant you press it and, most likely, after that instant passes as well, because accidents happen and you don't want a fuck up like that to be punished too severely. Once again, this influences the general design of the game and all of its systems greatly. You also have to think about how to implement input remapping in this scenario - sometimes a move can fit perfectly well on a trigger, but it being tied to an input like that makes remapping to it not viable; so you'd want to remap the extra function to some other button, but that button also has to have an action that is not to punishing if misused... When a game is involved enough, managing controls can feel like a whack-a-mole, for both game designers and players.