In the computer fighting game Big Bang Beat: 1st Impression, you have an energy meter which depletes as you attack, and disables most of your attacks when it drops low enough. You can recharge this meter using the classic SNK "stand still and hold down a button" method: However, you have to HOLD the button to charge. The computer, which IS limited by this bar as well, tends to TAP the button, meaning they charge with at best a tenth of the speed you do, and most of the time fail to charge at all. Thus, you can usually win any fight by turtling until the opponent's bar runs out, and then bashing him to pieces as he futilely tries to recharge.
Several recent WWE SmackDown! vs. RAW games exhibit problems during specialty matches, most notably the Elimination Chamber — rather than fight normally, computer-controlled opponents will instead spend much of the match climbing up and down the chain rigging and corner chambers. Sometimes, rather than climb down, opponents will instead hurl their bodies off the chambers with diving attacks that almost always miss, inflicting upon them damage more grievous than the player-controlled character can effectively dole out. However, they do make up for this somewhat by constantly breaking pin attempts — despite the fact that the Elimination Chamber is an elimination-style match and the computer, at least in theory, benefits from the elimination of other competitors just as much as the player does. Meanwhile, AI characters in the Royal Rumble mode have been known to eliminate themselves from the match by jumping onto an opponent outside the ring.
These problems have been resolved - the Royal Rumble having been overhauled, while the Elimination Chamber was fixed in that regard (though still tends to have one major glitch a year) - but now there are others. Three in particular come to mind; first, computers will about 50% of the time go running after any ladder that's outside the ring immediately after it's put there, which in a Money in the Bank match can get you alone in the ring with another ladder to try and climb up - if you do start climbing they will come back, but it does give you some precious seconds to give it a shot. Second, computers love to throw you into the corner and turn you around over and over and over again until you recover, rather than actually attack. And third, in a Scramble match computers will always move to break up any pins, even though on paper the only person who would be affected by it would be whoever the current champion is.
In defense of the Scramble match glitch, in the Real Life matches, superstars would often break up pins even though they did not gain or lose anything for doing so.
WWE Raw 2 on the Xbox combined this with Obvious Beta. In almost every match the AI would attempt to pin your character the first chance it got. As in, it would do a grapple to get you on the ground then attempt a pin 4 seconds into the match. Whilst this is occasionally Truth in Television what would happen next is not. The player would mash the buttons to break the pin and then before they could recover the AI would attempt to pin them again. And again. And again. It was not uncommon to see matches reach the 20 minute time limit and end in a draw simply because the player was stuck in a cycle of infinite pin attempts.
Despite being an SNK Boss on the last floor of the Tower of Souls, Algol in Soul Calibur IV has an exploitable AI: he tends to perform a low slash followed by a leaping low slash when he knocks your character down. If you happen to be lying on the edge of the arena, odds are he'll leap to his doom.
The FightingGame Maker, M.U.G.E.N, being accessible to amateurs and highly popular, has AIs that fall everywhere on the scale. On the one hand, you have ones that make the official SNK Bosses look easy; on the other, somewhere out there, there's a Zero character with an AI so badly written, it will actually crash the game.
In counterpart, there are some characters (and AI patches for SEVERAL characters) out there with an AI so well-coded that makes it almost look like you're playing against a pro, averting this trope.
Killer Instinct Gold features an odd version including Glacius's Liquidize move: Oh higher difficulty matches most enemies read your moves and perform specific moves to keep you from starting combos. If you are all the way across the screen, Liquidize briefly, and simply remain still afterward, almost all opponents walk towards you until they are in range to do their specific counter-maneuver for Liquid Uppercut. No matter the opponent, their chosen move is always countered by Cold Shoulder, Rock-Paper-Scissors style. As long at it goes into a simple combo, they will rarely be able to do anything else. This actually gets EASIER to do the farther you go and the harder the setting.
In the old Ranma1/2 fighting game Super Hard Battle, final boss Herb invariably responds to projectiles by jumping over them and towards the opponent. Therefore, defeating him is as simple matter as using a projectile, hitting him with an anti-air attack (knocking him back to almost the exact spot where he started), and repeating.
The AI in Jump! Ultimate Stars for the DS is the worst fighting AI short of MUGEN. The AI is so bad that most players recommend that people DO NOT BUY THE GAME if they don't have access to Wi-Fi. The AI will kill itself more often than you can kill it! The AI in JUS will jump to their death repeatedly in just about any stage with a pit in it, even after they've just respawned!
Let's not forget status effects. Auto-Run and Burn will cause the AI to do nothing but run straight ahead (even into a pit or wall) and Confusion makes them do the same thing but in reverse. Blind, Guard Seal and Movement Seal (which only seals your directional movement and jumping, not attacking or blocking) will cause the AI to do nothing but stand still, not even blocking.
Then there's their attacks. In a game with 50+ playable characters and over 200 Support characters, it seems that the best strategy the AI can come up with on any difficulty is to randomly mash the "touch" attack, launch Support characters at random intervals (even where it would be completely stupid to do so, like setting down a healing support when they're standing right next to you, and not picking it up) and repeatedly throw out projectiles and Specials with no regard to distance or actual effectiveness.
The game can also fall into The Computer Is a Cheating Bastard territory on Hard mode, where the AI will automatically block the second you touch any attack buttons. It still can't kill you, and still kills itself repeatedly, though.
In Melee there was something called the "flipper dance": when fighting a single computer opponent, pick a stage with decent sized flat base and no movement affecting gimmicks, such as Final Destination, take a flipper and just throw it straight so that it lands at walking height between you and the opponent and just stand still a few feet behind it. The enemy will slowly walk towards you, then, right before hitting the flipper, will dodge roll backwards, then start walking towards you again, rinse and repeat until the flipper expires. It never gets old to watch the computer completely forget it can jump.
They're similarly unable to comprehend bumpers in Brawl.
In the same game, some characters like Captain Falcon and Ganondorf will randomly throw out their strongest, but slowest attacks while you're nowhere near them, presumably hoping you'll just stumble into them. A player using Roy can have a field day with them thanks to his Counter special.
Some characters, like Mr. Game and Watch and Yoshi were particularly dumb, as they'd invariably approach you by performing a dashing attack or grab that would whiff if you just stood still, leaving themselves wide open for an attack. Therefore, it was possible to beat them without even moving.
Also, characters with an ascending Up B attack like Captain Falcon and Mario, would almost always use that move if you jumped directly above them from a distance. This would either leave them wide open for a retaliatory attack, or if they were standing at the edge of the level, potentially send them flying to their doom.
In Brawl, the AI can navigate custom stages fairly well...unless it has spikes. CP Us don't quite seem to get the idea that spikes are bad, and it's not uncommon to see a CPU work his damage up hundreds higher than normal just bouncing on spikes.
Trampolines also. If you're on one side of a wall and the CPU is on the other, it will spend tons of time trying to jump over the wall, even if it's too high, despite there being a spring behind it which it could use to jump over the wall.
It has trouble with the falling blocks, too - it doesn't seem to have any foresight, so it will often remain standing on a block until it's too low to reach the rest of the stage.
They do realize the spikes are dangerous, when they're about one inch away from them and unable to do anything about it. Same with a few dangerous items, where they constantly approach the item only to roll away from it just before they get hurt.
In general, they have trouble with the idea that stages aren't always completely static. If the bottom of the stage is occupied by horizontally moving platforms, the computer-controlled characters will miss the platforms by a mile every single time.
Throughout the series, no matter how high you set the computer's skill level at, they always make the mistake of walking onto motion sensor bombs no matter how visible they are.
Made funnier in Brawl by the fact that they'll briefly hesitate before doing so, as if contemplating whether it's a good idea or not.
Let's not forget Luigi's infamous glitch in Melee, where he would use his side special (which propels him horizontally as a missile) whenever he fell off the stage and usually fail. If he had used his up special (a big vertical jump) he would have survived, but the programming doesn't let him do so. The problem was that Luigi had two recovery moves, but the AI could only be taught one per character. This was fixed in Brawl.
In Melee, if you select Ness as your opponent, and select Jungle Japes, if you don't move at all Ness will perform a double jump straight into the river, regardless of what the AI level is (however, if you set the level to a higher one, he'll attempt to use PK Thunder, which ends up hitting the platform you are standing on). This was fixed in Brawl where he does the exact same thing, but manages to grab onto the edge of the platform and climb up.
There's an infamous video somewhere on YouTube of a level-9 CPU-controlled Fox continuously hurling himself into the river in Jungle Japes over and over again in the exact same way while the player (playing Luigi, of course) never moves from their starting point.
In Melee, if you play on Hyrule Temple and select any number of Kirbys as your opponent, you could effortlessly trick them into turning to rocks directly above the hole that goes down to the lower levels of the stage, in which case they would slide all the way down the slopes and into the pit.
Even a level 9 CPU Marth can act extremely stupid in Melee. Select him as an opponent and play on the Jungle Japes stage. Knock him off the stage once, and while he's respawing, quickly get onto the platform at the far right of the stage. Your opponent should jump toward you each time he respawns, only to perform his up+B special away from you, killing himself.
In Brawl, the AI will always perform an air dodge immediately after being struck in air, or being hit into the air, oblivious to the fact that there's a brief window of vulnerability as one ends. It's quite easy to juggle them to death by simply timing your attacks.
In Melee, some giant characters you go up against in one-player mode (specifically Yoshi) may start the match off by leaping off the edge of their platform into a Bottomless Pit, ending the fight in less than 5 seconds. It happens in Brawl too, but less often and usually a little later into the fight. Metal characters also suffer sometimes; they drop faster but the AI doesn't always acknowledge that.
In one Street Fighter game, the AI character of Balrog would react to many moves by trying to jump over them and punch you. E. Honda's hundred hand slap would cause him to keep jumping into it until he was dead.
It gets funnier: In every iteration of SFII prior to Super SFII, Balrog/M. Bison would routinely perform his array of dash punches and hardly anything else. This would lead to him being easily countered by a sweep attack or projectile attack. Similarly, Zangief could be defeated by simply backing into a corner and repeatedly jump kicking him in the head.
Some enemy AI is sufficiently designed to be ridiculously exploitable. For instance, against Ken in Street Fighter Alpha 3 or the Capcom vs. SNK: Millennium Fight 2000 games, jump backward and attack. If he has enough meter, he will do his Shoryureppa and miss completely. Similarly, the final form of Bison in Alpha 3 can be easily baited with a jab, against which he will either teleport behind you (easy to combo or super) or crouch for a few seconds and throw a fireball (easily jumped and comboed).
In Ultimate Marvelvs Capcom 3, when repeatedly using Doctor Doom's Hidden Missiles special, CPU controlled opponents will only block, even if they are standing within striking distance of a totally defenseless Doctor Doom. The CPU opponent proceeds to take chip damage until KO-ed. This occurs on even the hardest difficulty setting.
Rise of the Robots was touted in a pre-release trailer for the game as the first fighting game where the enemy adapts to your fighting style and changes its tactics based on how you come at it. This, however, is a lie, as every single opponent, up to and including the final boss, can be defeated simply by moving forward and kicking it into a corner.
In the Fighting Game spinoffs of Touhou, the AI pretty clearly has no idea what it's doing. It tends to spend most of the match running around, launching random danmaku and special attacks. This actually works kind of okay for certain characters, but plenty of them have attacks with limited range or specific uses, which the AI just doesn't get. The AI mostly gets defense, but tends to drop block the instant is gets out of blockstun, which can screw it over when fighting characters with dial-A combos that include a pause. And it'll never use skill cards or system cards, and spell cards only rarely. Oh, and the only combos it will pull off by anything except accident are the aforementioned dial-A ones.
The computer opponents in Windy X Windam almost never block anything, even at the highest difficulty setting. In most cases, this allows characters with launcher attacks to lift the opponent into the air and juggle them until they die.
Unless they're lying on the ground, they won't think to block or dodge multiple-hit ranged attacks (especially super moves, which activate after a two-second delay).
In the higher difficulty levels of Dragon Ball Z Budokai 3, AI opponents are much more likely to try and use ultimate moves on you, which are difficult to connect against a moving target and a huge drain of ki. If you go purely evasive once they activate hyper mode, you can usually wait for them to run out of ki, then utterly thrash on them while they recover. If you get good at this, the harder levels can be easier than the normal ones.
Likewise, the strongest AI is programmed to attempt to out-teleport counter the player no matter what. Such a teleport consumes one energy bar, so a savvy player can get an energy advantage, then lure the AI into a teleport chain for the sole purpose of depleting their energy. Considering strong hits cause transformations to revert while under a minimum of energy bars, this was a huge issue.
In Dragon Ball Z: Supersonic Warriors, the AI seems awfully good at breaking the player's guard or countering, but once the player is stunned, they'll often stand still and do nothing. Although they sometimes do shoot a stream of ki bullets, they rarely finish the Z Combo with a strong attack.
In Ougon Musoukyoku, the easy mode AI puts up about as much of a fight as the training dummy for some reason.
It's especially apparent with Gabranth, who can't really do much outside of EX-Mode. Instead of charging EX-Gauge like a madman when you're not close enough to punish it, he just jogs back and forth.
Also, Exdeath. His whole fighting style is centered around blocking and countering. The A.I. doesn't seem to grasp that concept very well and instead of patiently waiting for you to make a mistake just spams slow and predictable attacks.
The A.I. also seems to have problems with dodging certain attacks, like Yuna's Mega Flare (if the enemy is standing on the ground) and especially Feral Chaos's Via Dolorosa - dodging it is hard even for a human player, making it the sole reason for him being banned in tournaments.