Behold the tales of Pokémon bosses, Gym Leaders, and Grand Masters for whom lulz at the player's expense flow more readily than the water in the Eclo Wastes. To make a long story short, these are the reason why Gym Guides exist.
NOTE: Final Bosses and Wake Up Call Bosses are not allowed unless they're overly difficult by their standards. Bonus Bosses are not allowed; they're optional and have no standards for difficulty. Battle Frontier/Pokémon World Tournament/challenge area bosses count as Bonus Bosses, so same rules apply.
Lt. Surge in Yellow has only one Pokémon, which is his Raichu. Easy, right? Wrong. First off, it knows Thunderbolt, which hits incredibly hard, especially at this part of the game, and it hits even harder than usual due to STAB. And to top it off, Raichu is at level 28, much higher than anything you've faced at this point in the game. It also has Mega Punch and Mega Kick, both of which hit incredibly hard and will do a number on Pokémon with lackluster defenses. To make it even harder, Raichu is one of the fastest Pokémon in the game, meaning that you probably won't have anything fast enough to hit it first.
Erika might not seem like much trouble, but if she manages to get the first attack in, be prepared for her to spam the single most annoying attack of Gen 1: Wrap. Unlike the version of the attack you're now familiar with, Gen 1 Wrap prevented your Pokémon from taking any actions while they were caught. And guess what she'll do the moment your Pokémon is free from her Wrap attack. That's right, use Wrap again, preventing you from doing anything more than watching as the attack chips away your helpless Pokémon's health at a painfully slow pace to add insult to injury, and God forbid she manages to paralyze your Pokémon while they're suffering Wrap. You'll essentially be stuck in an infinite juggle.
Sabrina at Gen 1. Her team of Psychic-type Pokémon is fifteen to eighteen (depending on which version you're playing) levels higher than the last gym leader. It doesn't help much that Psychic-types were also extremely overpowered in Gen I due to a glitch making them immune rather than weak to Ghost, contrary to in-game advice and Nintendo's own guides, and a poorly-balanced elemental system in which Psychic's only weakness, Bug, had lackluster Pokemon and moves. To rub salt in the wound, the only Ghost types at the time were also part-Poison, creating a vulnerability to Psychic moves.
Whitney from Gen II. Her Clefairy isn't particularly difficult unless it gets lucky with Metronome or locks you into a useless move with Encore, but her Miltank...oh lord. Its Rollout attack is an already-strong Rock-type attack that gets stronger every consecutive turn it connects, and lasts up to five turnsnote The move's attack power doubles its previous value from hit two onward, meaning on the fifth consecutive hit it's doing 1600% of its base damage. At this stage in the game, Rollout can put the hurt on pretty much anything, even if it resists Rock. Miltank also knows Attract, which can infatuate male Pokemon and give them a 50% chance of not attacking every turn, Stomp, a strong STAB attack with a chance of causing flinching, and Milk Drink to restore health. Just to top it off, Miltank is surprisingly fast and has enough bulk to give most physical attackers pause.
Trying to win the fight with any male Pokemon is pretty much hopeless because of Attract. It doesn't help that vast majority of the more powerful Pokemon in the game, including all of the starters, will almost always be male (the chances of getting a female starter are very slim; about 12.5%). But even if you do manage to get your hands on a female Pokemon, there's the extremely unfortunate fact that in the Gen II games, females are saddled with extremely low attack values, making them almost totally useless in battle. Thankfully, by the time the remakes came around, equality had been achieved, and gender no longer has any effect or relation to a Pokemon's stats (meaning females are just as powerful as males). However, with many species, females are still very rare and difficult to obtain.
In HeartGold & SoulSilver, they gave her the ability "Scrappy" (how appropriate) which allows it to hit Ghost-types with Normal-type attacks. On top of that, they gave it a Lum Berry as a hold item, giving it the ability to remove whatever status ailment you inflicted upon it.
This is even referenced in the anime, where Ash takes Whitney on in a 3-on-3 battle, and Miltank takes all three of his Pokémon out in one Rollout, getting so strong that she deals a One-Hit KO to them, and Ash loses the match. This is a scarily accurate representation of how most fights against Whitney go. This song sums it up nicely.
In Gen II's remake, Bugsy can qualify for this if you're not thinking. Scyther gained a move called U-Turn, which takes Scyther off the field to protect him from retaliation. The real horror comes from a strategy with Scyther: Once Bugsy's two cocoon Pokémon faint, Scyther has a STAB 70 power Bug-type attack without drawback (and with Scyther's good attack stat spells trouble) and the other attacks get a boost from Technician, Scyther's ability.
Morty's Gengar was already strong, with STAB Shadow Ball, Hypnosis to put you to sleep, Dream Eater to Life Drain sleeping Mons, and Mean Look to prevent switching out. Then HG/SS improved it even further, with Levitate turning its Ground weakness into an immunity, and Shadow Ball running off Gengar's monstrous Special Attack, instead of its inferior Attack. If you don't have a mon that knows Bite, good luck.
Clair doesn't seem too horrible, with a team of three Dragonair in G/S/C or two Dragonair and a Gyarados in HG/SS. Sure, they have strong attacks, but the Dragonair go down easily enough to Ice-type attacks, and even Gyarados is something you probably came prepared for. Then, you run into her ace: Kingdra, a dual typed Water-Dragon. Kingdra is packing some serious heat in the form of Surf, Dragon Breath, and Hyper Beam - and it has the stats to use those as well. Even worse, thanks to its typing, it has one weakness - the very uncommon Dragon-type attacks. In HG/SS, Kingdra gets even more brutal, with Surf and Dragon Breath upgrading to Hydro Pump and Dragon Pulse, a held Sitrus Berry, and the Sniper ability, which boosts the damage on Kingdra's critical hits.
Karen of the Elite Four wasn't terribly hard to handle in the original, but in HG/SS, she can throw unprepared players for a loop. Murkrow can hit Fighting- and Bug-types hard with Pluck, force your Pokemon out with Whirlwind, and hit your Pokemon with Sucker Punch, Houndoom was gifted with Nasty Plot to send its already beefy Special Attack through the roof, Umbreon can use its sluggish speed to its advantage with Payback, and Gengar has Focus Blast and Destiny Bond.
Champion Lance has 6 Pokemon which ALL know the super-powerful Hyper Beam. His team consists of 3 under-leveled Dragonites, one of which has Outrage, which will easily take out most of your team unless you have a fast Pokemon with Ice Punch or Ice Beam, or a Steel type that can withstand the damage from it. They also know Thunder Wave, so chances are you'll be the slower one. His Aerodactyl is super-fast and has the flinch-inducing Rock Slide, which Aerodactyl ISN'T EVEN SUPPOSED TO LEARN in Gen2. Gyarados and Charizard will be the least of your troubles, but even they are quite annoying. In the remakes, he gets even harder. All of his Pokemon except for the higher-level Dragonite have flinching moves (Dragon Rush, Rock Slide/Thunder Fang, Air Slash, and Waterfall), and he isn't as prone to abusing Hyper Beam like he did before due to the requirement of a recharge, and the other moves on his Pokemon are so strong he doesn't need to anyway. Speaking of Thunder Fang, it is learned by Aerodactyl in case you think you can take it out with a Water type.
Jasmine in GSC/HGSS has two Magnemite and a Steelix, both of whom have rather high levels for that stage in the game. It doesn't help that Steel has a load of resistances, making her a tricky fight for the unprepared. On the bright side, if you picked Cyndaquil as your starter, the hell Miltank put you through before will pay off here.
Chuck uses many variations of the Focus Punch strategies (some that are used by many competitive battlers) to make him terrifying. His horrifying Primeape in HG/SS will spam Double Team, then Focus Punch you to death. And it's pretty fast as well.
Blue in HeartGold/SoulSilver. Your team will be nerfed by Exeggutor's Trick Room, making the slowest Pokémon move first. The Mighty Glacier aspect of Pokémon like Machamp and Rhydon is thus conveniently removed, allowing them to destroy you. Of course, if you choose to rematch him, he turns out to have gotten a Tyranitar. Oh crap, indeed.
Bruno of the Elite Four in the remakes has a Machamp with No Guard, which allows it to still hit your mons even if you use a move like Fly or Dig. Just be thankful it uses Cross Chop instead of the universally-feared Dynamic Punch.
Brawly is the second gym leader you face in the game, and this guy hits hard. In Ruby and Sapphire, his first Pokémon is a Machop that knows Leer to lower your defenses, Bulk Up to raise its attack and defense, as well as Karate Chop and Seismic Toss, two fairly strong moves at that point in the game. Then Brawly sends out his Makuhita: A rather bulky bruiser. In Emerald, his Makuhita knows the super-powerful Vital Throw, along with Reversal, which is a move that becomes stronger when Makuhita's HP is reduced. One of the main problems when fighting him is the absurd jump in levels between the first gym and his gym, which is nearly right afterwards.
Wattson, especially in Emerald. He uses four Pokémon, all of which know Shock Wave, an attack that NEVER misses. Plus, all of his Pokémon get STAB on it, essentially turning it into a Thunderbolt with perfect accuracy. His various Pokémon have moves like Selfdestruct, a sacrificial attack that is five times as powerful as the standard Quick Attack (and that's without the fact that it halves the defense of the target in Gen 3); Rollout, a move that becomes more powerful after every successful hit; Thunder Wave, an ability that halves a Pokémon's speed and makes it unable to attack half the time; and Sonicboom, a move that ignores-type effectiveness and can destroy any opponent in two or three hits. To top it all off, his Voltorb is actually too low-level to learn Rollout or Selfdestruct, both of which it somehow has.
Flannery. Her first two Pokémon are easy enough but, like Whitney, she has a hell of a third Pokémon to back them up. Her Torkoal is incredibly bulky, and hits incredibly hard with its signature move, Overheat. Even though it lowers its special attack stat when its used, she has it equipped with a White Herb which brings her stats right back to normal (only once, but that's really all she needs). A smart strategy would be to lower her stats beforehand, causing her to use up the White Herb immediately! ...Too bad her ability White Smoke prevents this. She also knows Body Slam, which is not only powerful, but is likely to paralyze you (and this being the AI, it happens pretty much all the time). And to make this nightmare of a battle worse? She knows Attract, which makes it so male Pokémon are much less likely to attack her. It doesn't help that her other team members are likely to set up with moves like Reflect, Light Screen, and SUNNY DAY (which boosts fire moves and weakens water moves).
Norman. This guy is only the fifth gym leader, yet he has two Slaking, which have the highest attack stat of any non-legendary Pokémon up to then and a ton of HP. Even though they can only attack every other turn, they are still capable of KOing a Pokémon in one hit. He also has a Vigoroth, which is less powerful but pretty fast, able to attack before most other Pokémon you probably own, and isn't crippled by Truant. Finally, all three Pokémon come equipped with Facade, an attack that doubles in power if the user is poisoned, burned, or paralyzed. Norman in Emerald isn't too shabby either. He may have replaced one of his Slaking with Spinda and Linoone, but those two can certainly be annoying in their own way.
Winona is basically the Whitney of Gen 3, having a fairly easy team up until her very last Pokemon, and it's a doozy. Winona uses Flying types, and her last Pokemon is an Altaria which knows the deadly combo of Earthquake and Dragon Dance, which she can't learn at the level you fight her, setting her up perfectly to sweep your entire team with powered up Earthquake and Aerial Ace techniques.
Tate and Liza in Emerald. It's fought in a Double Battle, a brand-new mechanic not seen much prior to this fight, which requires much more strategy than Single Battles. In Ruby and Sapphire, their team only consisted of two Pokémon (meaning you could, in theory, defeat them in one hit). This time around, however... You first need to fight through a Xatu (which can either use Confuse Ray on your fighters or Calm Mind to jack up its stats, aside from flat-out attacking with Psychic) and a Claydol (which spams Earthquake and AncientPower). The best part? Earthquake hits everything on the field, but thanks to their team choices, you're the only one who will get hit by it. Then there's Solrock and Lunatone you have to deal with. Solrock will use Sunny Day to power up its Flamethrower and instantly use SolarBeam, as well as jacking up its stats and attacking with Psychic, while Lunatone will put up Light Screen (Claydol knows it, too) to raise the opposing team's already high Special Defense, put you to sleep with Hypnosis, and do the same Psychic/Calm Mind combo. The team is also prone to using moves (such as the aforementioned Claydol's Earthquake) that hit both of your Pokémon at once, raising the stakes that much higher.
In Emerald, Juan. He starts out with his Luvdisc, which has a lot of Speed and loves to spam confusion (and Attract if your Pokémon is male) - terrible stats apart from Speed don't matter much when your Pokémon is busily killing itself. And that's just the starting point - his other Pokémon will be quite happy to Rain Dance, boosting the power of their Water moves to ridiculous levels (and as an added bonus, doubling the speed of any his Pokémon with "Swift Swim"). Whiscash hits hard with STAB Earthquake, and his Sealeo is all too happy to annoy you with the seldom seen but incredibly nasty Encore. Of course, all of this pales in comparison to his trump card: Kingdra. It has the ability Swift Swim, meaning that while it's raining, outspeeding it is nigh impossible, and that's on top of the rain boosting its power. It also uses the obnoxious Chesto-Rest strategy, allowing it to fully heal its HP and remove status at no cost (but only once; of course, after that once, Juan is all too happy to use Max Potions when its HP gets low). Did we mention Kingdra also has DoubleTeam? Have fun with that.
You were led to believe Steven only trained Steel types, but you were led wrong! His very first Pokémon, a Skarmory, has Spikes, which deals damage to any Pokémon you switch in (provided they aren't airborne). It also has Toxic, a Poison type move that gets worse each turn. To make matters worse, his Claydol knows Light Screen and Reflect, which increases the already high defense of all his Pokémon even more. He also has a Cradily who has excellent typing as well as great bulk with great type coverage (Giga Drain, Ancient Power, and Confuse Ray). On top of that, his ace is Metagross, a steel/psychic Pokemon with great type coverage (Meteor Mash, Psychic, and Earthquake).
If you chose Piplup, good luck defeating the Withdraw spamming Turtwig in the first rival battle.
Fantina is one of these. Her Pokémon have powerful Psychic-types moves that can easily mess you up pretty badly. In Platinum, her first two Pokémon are pretty easy, but the Mismagius can easily wipe you out.
Cyrus's battle in Spear Pillarnote Diamond / Pearl / Distortion World note Platinum. Gyarados used Aqua Tail / Waterfall! Bam, you're dead. Reload. Gyarados used Earthquake! Bam, you're dead. Gyarados used Ice Fang! Bam, you're dead. His Crobat just as bad. Confuse Ray to throw you in for a loop, Air Slash to flinch, which is likely to happen, and Toxic just to make it more painful. Weavile, Cyrus's strongest Pokémon, has high ATK and Speed. He will be able to demolish your team quite easily thanks to his high coverage, with attacks like like Night Slash, X-Scissor, Ice Punch, and depending on the version, Brick Break (Diamond / Pearl) or Fake Out (Platinum). Honchkrow has a mix of attacks, especially in Platinum. Houndoom in the Platinum version is the least of your worries, but it can pack quite a punch with Flamethrower and Dark Pulse. It also has Thunder Fang, in case you were trying to use a Water-Type against it. His team movesets are much better than what you have faced up to that point as well, so... less to be said, Cyrus's team is quite the thing for that point in the game.
Flint. His Infernape is outright terrifying due to its high level and great coverage (Flare Blitz, Thunderpunch, Earthquake, and Mach Punch). He usually starts off with Sunny Day, and then the "fun" really begins. His Infernape's Flare Blitz combined with Sunny Day will pretty much instantly defeat anything and even then he still knows Earthquake. He's no slouch in Platinum either. If his Houndoom or Rapidash manage to use Sunny Day, you're in trouble. Rapidash is pretty damn fast.
And then there's Lucian, who directly follows Flint in the Elite 4. He's a Psychic-type user, and his team is nasty. Mr. Mime using Reflect and Light Screen will stop your one-shots. There's also Alakazam, with huge speed and special attack, and then there's his Bronzong. Bronzong has "Levitate", meaning your Ground-Types won't help you, meaning its only weakness is Fire. Oh, and it can throw Earthquake at you too.
The champion battle with Cynthia is by far one of the most difficult fights of the franchise. Her team is very highly leveled even compared to the fight immediately before her, has varied types, and boasts perfect IVs across the board, meaning that they're far stronger than normal Pokémon you might fight at the same level. She has Spiritomb, which has no weaknesses to any types; you just have to have a mon strong enough to hit it until it dies. And then there's her Garchomp, a monster of a Pokémon that is so utterly overpowered Smogonbanned it from its competitive play rules altogether during the 4th gen competitive metagame. (Even if that ban was because of one of it's abilities, Sand Veil, which gives it a massive evasion boost.)
Gen V follows the tradition of Normal-type Gym Leaders being That One Boss with Lenora. Her Watchog knows Retaliate, a Normal-type move with a very respectable base power of 70. However, if a Pokémon in the user's party faints on the same turn, it doubles to a whopping 140, and that's not even counting STAB. Since Watchog will always be Lenora's second Pokémon, it can Retaliate right after you defeat Herdier, and it can OHKO pretty much anything you throw at it. It doesn't stop there, either. Her Watchog knows Crunch, a very powerful move at that point in the game, and can put your Pokémon to sleep with Hypnosis. Herdier is no pushover either, having stats comparable to Watchog's and knowing Take Down, which hurts a lot coming from a Normal-type. It also has Retaliate, if you feel like using Roar to take out Watchog first.
Likewise, Black and White 2 gives us the first Gym Leader, Cheren. All his Pokemon know Work Up, and while his Patrat isn't that big a deal, his Lillipup is. It'll probably be faster than you, and if it sets up the Work Up, there's little you can do once it uses it once or twice, and it'll probably sweep your team. And in Challenge Mode he has a Pidove whose only attack is Quick Attack, and paralyzing that won't do you much good.
We also have the fourth Gym Leader, Elesa. She uses two Emolga (Electric/Flying) and one Zebstrika (Electric). Her two Emolga know Double Team. Then her Zebstrika is so fast and so strong it mows down anything that comes in its path. And all three get Volt Switch, which does reasonable damage and switches them out.
Elesa even has the dubious honor of coming after anotherThat One Boss: N. Or more specifically, his Sigilyph, which has insane stats for that section of the game - its Speed is high enough to nearly guarantee it the first strike against anything you throw at it, and it knows Tailwind to eliminate the "nearly". Its Special Attack is high enough to virtually guarantee a One-Hit Kill on pretty much any Pokémon. Think it's a Glass Cannon? Not at that point in the game it isn't. It also has Magic Guard.
Even within the Elite Four, Marshal can be pretty difficult, because all his Fighting-types have very high attack. His Sawk has Sturdy, which keeps you from OHKOing it. Throh and Conkeldurr have big HP and will likely not be taken down without you receiving a big hit in return, and in the rematch, he has a Breloom with Spore (Black/White) or a Lucario and Medicham (Black 2/White 2), the former of which has high Special Attack, especially for a Fighting-type; and the latter of which has a devastatingly strong STAB Hi Jump Kick and the elemental punches. If you're about to die, Lucario will slam you with ExtremeSpeed. And on Challenge Mode, that Medicham is replaced with a Machamp that uses No Guard with Stone Edge and Dynamic Punch, the latter of which always confuses you. He's not a foe you want to mess around against.
Shauntal can be a pain considering most of her Pokémon have a secondary type, meaning that they're actually somewhat well-balanced in comparison to other Elite Four members. They also have high defenses (Cofagrigus and Jellicent/Drifblim), high power (Golurk and Chandelure, which have the highest physical and special attack stats of all Ghost-types, respectively), or are just plain fast (Froslass and Mismagius). Also, her Mismagius knows Perish Song. Be glad it doesn't know Mean Look. Challenge Mode gives her a Gengar instead of Mismagius, which is fast and can hit very hard with STAB Shadow Ball and Sludge Bomb. In that same vein, in both the initial battle and rematches, Chandelure gets a Choice Scarf, which boosts its Speed by 50% in exchange for locking it into the first move it uses until it switches out or dies, so if you're not high leveled it's almost guaranteed to get a hit off.
If your Pokémon happen to be kinda slow, Clay's Excadrill will likely wipe out your entire team. Made worse by the use of Hone Claws which increases Attack and Accuracy.
The Final Boss, Ghetsis, can be a real hair-puller, coming immediately after another difficult fight without so much as a chance to save — thankfully your Pokémon are fully healed between the fights, but this is still a trick the franchise rarely pulls. Some of his Pokémon are more deadly than others; Bouffalant can rip through whole teams with a powerful STAB move (and has amazing defenses), Eelektross is an Electric Pokémon with Levitate (which means no weaknesses) and has the offensive stats to do more than stall. But that's just preparing you for his worst: an underleveled Hydreigon. This thing is monstrous. Aside from the fact that it's almost certainly a couple levels above you, it has astonishingly good type coverage and perfect EVs and IVs.
In the sequels he doesn't let up much. His Cofagrigus has high Defense and will use Protect to guard and Toxic to wear down your team, and also can override your Ability when hit. His Toxicroak also is very strong and has an Action Initiative move in Sucker Punch. Drapion has high Attack. The Eelektross is just about the same as it was before, though it's got Thunderbolt instead of Wild Charge. And the Hydreigon? It's at a lower level (52, 56 in Challenge Mode) than before, but thankfully uses a less versatile, physical-oriented moveset (Dragon Rush, Crunch, Rock Slide, and Frustration).
Black 2 and White 2 throw a pretty hard boss at you in the Plasma Frigate, in the form of Colress. His first Pokémon is a Magneton. It has Sturdy, so you can't OHKO it and it will proceed to Thunder Wave you. To add on to that, it holds the Eviolite, which boosts its Defenses by 50%, so it's bulky, too. Next up, it uses Volt Switch to get out of there while hitting you rather hard. His Magnezone has Sturdy and Thunder Wave too, so beware that. He also has a Beheeyem with Calm Mind that can boost up and hit you pretty hard, and a Klinklang that boosts up with Gear Grind. He even poses a bigger challenge than the team Ghetsis uses in a later fight.
For the Champion, Iris is quite more difficult than the previous Champion. The first Pokemon you're up against is another underleveled Hydreigon. It will plow through your team with Dragon Pulses, Surfs and Flamethrowers, which hit everything in the game for at least neutral damage.note In the rematch teams, her Hydreigon's moveset is the exact same as Ghetsis' first Hydreigon. Then, once you get through that, you'll have to fight through an Archeops, which is fast and hard-hitting; Lapras, which has high HP and defense and knows Sing; Druddigon and Aggron, who are just tanky in general; and then Haxorus, which has a ton of powerful moves and Mold Breaker. note The rematches give it Guillotine and Outrage.
And Arceus help you if you're playing on Challenge Mode, because her team gets a complete redesign. Each of her Pokemon gets at least one of their moves replaced with a more damaging alternative and get held items that either boost the power of their moves or accuracy. But the most dangerous change is Druddigon being replaced with a Salamence holding a Life Orb.
Siebold. More specifically, his Gyarados. Even more specifically, the fact that it knows Dragon Dance. It will easily achieve a Total Party Kill. It also has good coverage for its weaknesses: Earthquake for Electric-Types and Ice Fang for Grass-Types. The rest of his team is no slouch either: Clawitzer has very wide coverage with Mega Launcher-boosted Dark Pulse and Aura Sphere, Starmie is extremely fast and packs Dazzling Gleam for any Dark-types (and Dragons) that would try killing it, and Barbaracle is a powerful physical attacker.
Grant, the second Gym Leader, can be considered one of the tougher ones in the game. First off is his Amaura, which may have a lot of weaknesses, but is decently bulky for this point in the game. It can hit pretty hard, with its Refrigerate ability not only turning its Take Down into an Ice-type attack, but boosting it by 30%, effectively making it a 171 power attack. It also packs Rock Tomb to lower your Speed, alongside Thunder Wave. Then there's Tyrunt, a part Dragon-type, and it too has Rock Tomb to lower your Speed. Then it has Stomp to possibly flinch you afterward, and Bite which is the same but is even stronger thanks to his Strong Jaw ability. His team might have a lot of weaknesses, but they're durable and hit hard to counteract that.
While she's not difficult, Viola can easily surprise players who were hoping to incinerate her Bug team with Fennekin or Litleo. Her first Pokémon, Surskit, is Bug/Water and thus neutral to Fire moves. It also knows Water Sport, which will weaken Fire-type moves so that her trump card, Vivillon, will barely take any damage from her. Both Pokémon also know Infestation, which can wear down your Pokémon surprisingly fast. Ironically, players who started with Chespin will likely have the easiest time against her, as it learns Rollout early on and can easily plow through Vivillon who will take 4x damage from it.
Clemont can also be tough for those who think they can rely on type advantages. His start-up, Emolga, can completely evade Ground types, use Volt Switch to evade and switch-out, and paralyze you if you use contact moves due to its ability. Heliolisk on the other hand, knows a Grass-type move to counter any Ground-type Pokemon you will bring up. Magneton also knows a STAB special Steel-type attack which can hit decently and also lower your accuracy, and has the ever so annoying Sturdy ability. And all three hit hard with Thunderbolt. In short, you can't just rely on type advantages alone; you will need to be able to strike first and effectively exploit any stat weaknesses Clemont's Pokemon have.
A minor one would be Wikstrom. Due to the secondary typings, not all of his mons share a single weakness and he is somewhat hard to sweep. He will lead with Klefki which has Prankster, meaning it is very likely to set up a single layer of spikes or use Torment on you before you can kill it. His Probopass has Sturdy and a good array of moves, his Scizor has Technician + Bullet Punch, and his Aegislash can switch modes back and forth via Sacred Sword/King's Shield, which lets it hit hard and tank.
The final battle against Lysandre may be one of the toughest villainous team leaders yet, having strong Pokemon at very high levels for the point in the game you encounter him. Of course, this isn't helped by him also using Gyarados or rather Mega Gyarados, which wields a variety of powerful attacks with insane type coverage.
For the Super Training Mini-Game, the special attack boosting Magnezone often trips up new players. Its targets constantly move in a circular pattern, and unlike similarly mobile enemies, it fires waves of homing projectiles that force the player to maneuver and readjust aim.
Team Rocket of all opponents, is easily one of the toughest opponents you'll face. Right before you try to gain the Earth Badge from defeating Giovanni, Jessie, James, and Meowth ambush you and force you to face them first. Ironically as opposed to most games where they're defeated easily, in this game they are a major threat and know how to chain combos like nobody's business as they can easily hit a 10+ combo even on lower difficulties which is usually enough for an instant victory, and they're even worse on harder modes. The Giovanni battle right afterwards while formidable is nowhere near as difficult as the previous battle.
The last boss, Gary, is incredibly difficult even for a final challenge, as he is quick and easily makes multiple chains for major damage on your side of the field before you can react. It gets even better when you defeat him on hard mode and you face the True Final Boss, Mewtwo, who is a much more difficult version of Gary. The best part about this whole ordeal is if you lose against the True Final Boss (which is very likely), you have to defeat Gary all over again.
The reward for defeating Hard Mode completely is accessing Very Hard Mode, where everyone hits this status. And then, if you beat that, you get access to Super Hard Mode, where everyone becomes an SNK Boss.
Charizard in the first game. The second time with him is a lot harder. Not only does he like to fly around while blowing flames, but his fireballs scatter much more densely, making it hard to circle him — and even with assists, it takes a lot of loops to get him. It also doesn't help that if you take too long, he flees the battle and you have to start all over again...
Several players have a pretty rough time with Steelix, too. Even when he coils up (which is about the only time that circling him is even possible), his sheer size makes drawing those loops awkward. Having multiple Water and/or Fighting assists comes highly recommended.
Drapion is a rather irritating boss due to the fact that you face two group captures directly before it. And that you come to a full stop at one part unless you happen to have a Normal-type Poké Assist ready.
Flygon. You're not allowed any other Pokémon because it's a "test" and the bloody thing resists Plusle/Minun's assists. And it's incredibly fast, making it nigh-impossible to get the amount of circles you need to finish the battle.
Entei. Not only is it fought at the apex of a Sequential Boss gauntlet of all three legendary beasts, you have to deal with the fact that it basically attacks the entire screen. And in the refight, you can only bring three Pokémon for the whole thing...
Metagross can be a real pain if you don't have the right assists. It pretty much fills the screen with beams and makes shields for itself.
Regigigas in the second and third games causes damage just by WALKING. It's easy to screw up and lose and assisting Pokémon, and your Styler gets damaged if you don't circle the thing immediately before or after it launches an attack.
Ditto in Guardian Signs. You thought fighting each of the beasts individually was bad, this thing will transform into each of them over the course of the fight. Unless you have a variety of Poké Assists, you're in for a long fight.
Feraligatr in the third game. It's not so bad before and after it rages, but while it's raging, it tackles all. the. time. And 9 times out of 10, it will charge off screen so you can't circle it between attacks, not that there's much time in between for circling it. And each tackle does 10 points of damage.
Salamence in the first game. Like with Flygon, you aren't allowed to have other Pokémon with you. Unlike Flygon, however, it's slow but more than makes up for it by having to draw a ridiculous amount of circles around it (22, surprassed only by three Pokémonnote Meganium's 25, Metagross's 30 and PSYDUCK's 32). It also outright ignores your starter's assist, and likes to fly above the battlefield for long stretches of time, meaning you can't circle it. Simply landing counts as an attack, and it hurts.
The Cipher Admins are all That One Boss, not because they were difficult to defeat but because you had to spend ages trying to capture the legendary beasts while keeping yours alive. Don't forget the fact that, when you catch a Shadow Pokémon, all they have is Shadow Rush (at least in Colosseum, anyway)... but before you catch them, their original trainers can use all of their other moves. Hence allowing the aforementioned Thunderdance combo. It also means that there's a chance that your Shadow Pokémon-owning opponent could use Shadow Rush, which gives recoil damage. This means that someone trying to catch a Shadow Pokémon had to be very careful about the opponent's HP; leaving it at 1 HP or near it could leave it vulnerable to its own recoil. At least the Shadow Pokémon owners generally didn't use Shadow Rush, but that doesn't mean the possibility was gone. Thankfully, XD eliminated recoil except on a couple moves.
Ein has a Raikou with a damaging Thunderdance combo. He's also a big fan of inflicting the Confusion status, and as is usual for the Pokémon games, your team will suddenly become about 250% more susceptible to the detrimental effects of Ein's status ailments. You hopefully have Suicune and Entei then, but his water team will destroy the Fire-type Entei, and Suicune falls easily to Raikou's Thunder.
With Dakim, you had to try to capture the legendary Fire Pokémon Entei, who was weak to Ground moves. Guess what Dakim's favorite move was? That's right, Earthquake! Every one of his Pokémon had it, and got STAB bonus from it as it hit everyone else on the field, which meant that if Entei came out too early, it was going to get knocked out before you could catch it. If their constant Earthquakes didn't defeat you, the high probability of Entei fainting too soon would probably have you replaying this fight over and over again.
Miror B. has several Ludicolo that use Rain Dance to activate their abilities Rain Dish and Swift Swim, meaning either they regenerate their health or make them far faster than you. They are all fully evolved Pokémon at a decent level and have very few weaknesses you can exploit at that point in the game. Fortunately he's easier in the sequel, although he does have a Shadow Dragonite in the last battle.
The final boss, Evice, is pretty difficult, but generally par for the last boss of a Pokémon game. However, should his Slaking and Slowking end up on the field together at any point, you're screwed. Slaking's stats are equal to those of Groudon's. Slowking will use Skill Swap at the first possible chance, which gives it Truant and gives Slaking the ability to attack every turn. His other Pokémon generally have high attack stats, as well as moves that boost their strength to even higher levels. Special mention? His Scizor, who can Baton Pass Swords Dances if it isn't taken care of onto another one of his Pokémon; and his Salamence.
The second fight with Snattle in Pokémon XD: Gale of Darkness also hurts quite a bit if you don't have the right number (or quality) of sweepers. Why? Starmie. It hits fast, hard, and if you haven't been dragging a tank of a Shadow Pokémon around to soak up the damage, it can wipe out an entire non-Shadow team. Its Shadow Solrock partner, by contrast, is almost insultingly easy after that thing.
And even when you win, Cipher Peon Kleef proves Dangerously Genre Savvy by ambushing your team as you go through the Door To Before, while the next healing machine is through him or another boss and the last one is a major backtrack. Thankfully Kleef is otherwise pathetic (a team of stallers with no Shadow Pokémon to snag) and XD allows saving anywhere, but it really hurts when your team has such major injuries.
Thug Zook, when encountered outside the Key Lair immediately after the Snag Machine is stolen, is a nightmare. He has a Shadow Zangoose with him that is above the typical level for that point in the game, and it will happily kill off one of your team members every single turn, first, without fail. Essentially this forces you to constantly pick away at it with the survivor, hoping you have enough firepower to kill it before it wipes out your whole team, and then proceed to spam Revives and healing items while his other Pokémon are busy trying to kill you less effectively. It's so bad that in the rematch with him, his mons haven't leveled up at all, and he's still a very hard opponent to beat.
Grand Master Greevil can be this for the unprepared. Three Shadow Legendary Pokémon (the legendary birds) at Lv. 50+, plus another three relatively strong Shadow Pokémon (Exeggutor, Tauros, Rhydon) at Lvl. 46+. What this means is that powerful attacks will be headed your way, and every attack against you will be super effective thanks to the Shadow type, as well as a low catch rate for the Legendary Pokémon. If you're not prepared, you'll run out of Revives and/or Snag Balls before all six can be snagged.
Before him, there's one of his right-hand men as well as the penultimate boss, Eldes. He has four Shadow Pokémon, which will be the highest amount you've seen in the game so far, and they are all hard hitters. Special mention goes to his Marowak, who hits extremely hard thanks to its held item the Thick Club, and his Salamence, who is Level 50 at a point where your past opponents have been in the mid forites. Without a decently bulky Shadow Pokémon to absorb their blows, Marowak and Salamence will pretty much one-shot anything you throw at them. And to make things worse, all of them (save for his Shadow Manectric) are decently bulky as well, making them even harder to take down. If it's any consolation, his non-Shadow Ninjask and Flygon are nowhere near as annoying to deal with as the rest of his party.
Those bloody group bosses. I'm talking to you, Luxio/Electrike tribe, Dusknoir and Sableyes, 'The Grand Master of All Things Bad' and their cronies. And let's not forget Darkrai and pals.
Articuno in the first games. Its main attack is Powder Snow, which will hit both you and your partner and the damage is high enough to OHKO you. Not even Pokemon that resist Ice are safe from it, so unless you brought plenty of Reviver Seeds, this is a battle that pretty much rides on luck.
Primal Dialga is no pushover either. He packs a lot of HP. He's got a great defensive typing (Steel/Dragon). He's got the intimidator IQ skill, which more often than not prevents you from hitting him at melee range. And to top it off, he's got Roar of Time, which can hit both you and your partners from anywhere in the arena, is surprisingly accurate and deals triple digit damage (thankfully you can turn it into a double-edged sword via confusing it)...at a stage when you just reached triple digit HP, which means you'll really need those Oran Berries and Reviver Seeds. Oh, and did we mention that you fight in your unevolved forms and losing forces you to climb Temporal Tower again?
Darkrai. It's hard enough getting to him with Cresselia in tow, and he wouldn't be all that hard to beat, being considerably weaker than Dialga, were it not for the exact same Cresselia whose relatively annoying tendency to throw herself into battle with just about everything becomes a downright suicide attempt against Darkrai, to whom Cresselia has a weakness. No matter how hard you try to keep her safe behind yourself and your partner, she will simply move right next to Darkrai all over again, allowing Darkrai to destroy her in 3-4 turns, if you are lucky. And, of course, as soon as she goes down, you all teleport out. The only way to overcome this is to take out Darkrai before Cresselia can go down, which is quite difficult, or fill your bag with a lot of revive seeds.
The final battle with Munna and cronies is truly a difficult fight. Try to use a Wonder Orb to cripple the team? Not gonna work, they've got a Team Skill that'll wipe it immediately. It's also a seven-on-four battle. Munna herself will spam Hypnosis and Psybeam to inflict status ailments on you, and bulk up her defenses with Defense Curl (fortunately, Synchronoise, the other move she has, has no effect on anybody). Get put to sleep, and you're screwed; especially since you are closest to her. Toxicroak will spam annoying moves like Taunt and Swagger, Chandelure can confuse you (easily the most frustrating status ailment in the game), poison you, and hit you with Flame Burst, which deals an additional 10 damage to everyone in your party after hurting you. On top of that, the four Gigalith will spam Harden and Iron Defense to tank up their defenses, and may randomly survive fatal damage because of their Tough team skill. You will get stomped if you're not careful. Kyurem afterwards is almost a cakewalk compared to this.
During the initial story, Oichi warns you that Normal-types are weak to Fighting-types when attacking the Fighting kingdom Pugilis. It so happens you have to take your character and Oichi every time you attack a kingdom, and your two Pokémon are Eevee and Jigglypuff, neither of which you can possibly evolve at this point in the game yet. Right off the bat, two of your Pokémon are at a heavy disadvantage. And if you're new to the game and don't know the strategy for how to conquer Pugilisnote the map requires you to capture four flags on a center platform and hold them for five turns, with Pokémon on the edge of that platform being knocked off and having to go around to climb back up. This in mind you can blockade the paths onto the platform and let the timer run out, you're going to probably going to end up having to just fight it out until the enemy is all defeated, which ain't easy.
Taking Nixstorm is very difficult to conquer in any storyline. It's the Ice-type kingdom, and the battlefield is a large mass of Frictionless Ice like you know from the main games, making it very difficult for Pokémon to move around. Not that the Nixstorm warlord Mitsuhide cares, his Lapras is an Ice-type, as likely are the Pokémon of his allies, and they can move on the ice normally. You'll need Flying-types or Levitate to move normally (and remember Flying is weak to Ice), because Ice-type Pokémon of your own to use are not easy to find at that point in the game. And Mitsuhide's Lapras is very powerful with a nasty Ice Beam that can really hurt anything it finds in that icefield, and Shell Armor to block critical hits. Finally, on top of it all, in any storyline where Mitsuhide remains in Nixstorm, including the initial storyline, one of his allies has a Munna with Hypnosis.
In the original Stadium's Pika Cup, the 7th opponent (second to last) you have to face is a Lass who bends the rules to her favor. The ruling states that the total level of the three Pokémon you use can't exceed 50. The computer, thus, gives you a choice of lvl 15 Pokémon (and you must use these if you can't connect your own Generation I game to the game, especially now since neither game will save due to the save battery in almost all copies by now being dead). Lass, however, has access to two lvl 20 Pokémon, a Gyrados and a Tentacruel. She's only able to use one, but she only needs one, as either could devastate your party. Her party is also well balanced and unpredictable. Pick Hitmonlee to face her Dewgong or Meowth? Surprise, she sends out Mr. Mime. Oh, and this is her in Round 1.
Stadium 2's Janine. She's easy in Round 1, but what's her strategy for Round 2? Baton Passing multiple layers of Double Team (a move normally banned in Smogon competitive play for being too luck-based). All her Baton Pass targets can take a few good hits, have Confuse Ray, Attract, or Swagger to screw with your chances of hitting even further, and will wear you down with Toxic and Sandstorm. If you're planning to just switch out, take note that she's also packing Spikes and Mean Look. She will slowly torture you to death unless you come prepared with Haze and Heal Bell, but even then you're still at the mercy of many elements of luck.
Erika had a really annoying rematch Vaporeon because of the former ruling that Sleep Talk could pick Rest again to restore the health. Vaporeon having a ton of HP and decent special defenses did not help matters at all.
The Elite Four fights in both Stadium games. They consist of a gauntlet of five fights in a row, each very hard thanks to a mix between genuine difficulty and cheating on the AI's part, and if you lose, you have to start all over again. Losing to Lance in Stadium 2 when you were so close to defeating him is common, and insanely frustrating. It's sightly easier if you import your own tailor-made team from one of the main games, but if you don't have one or can't, you're stuck with using rental Pokémon, which make the fights a hell of a lot harder.
Sashay from the "little cup" Sunny Park Colosseum in Battle Revolution. Especially her Treecko. That stupid thing spams Energy Ball like there's no tomorrow. A big attack like that on a little baby is a big surprise for those who aren't prepared!
Everyone becomes That One Boss on the "Level 50 — Rank 8" setting. The boss of the Colosseum will throw uber legendaries at you just to screw you over. "Colosseum Leader Taylor sent out KYOGRE!"—cue rage quit—And it's not just the bosses! On rank 8, everyone leading up to the boss will use 3 legendaries at the very least.
And don't even get started on Mysterial and his annoying Chansey! Kingler, Golbat, and the rest are bad enough, but that Chansey is Normal-Type and hard to take out.
The Courtyard Colosseum boss. His team varies due to the nature of the round-you and your opponent both select rental Pokemon from a pool-, but he usually has a Vigoroth. It has good stats to begin with, and it loves to OHKO or severely damage as many as it can of your team with Body Slam or Brick Break. Plus, it's Normal-type and resists everything but Fighting moves. If you choose Machop, you have fighting moves, but Vigoroth always seems to move first and remove the option. Then he has Gabite. You can damage or eliminate it with your own Gabite or Gible, but he usually gets Dragon Rush off first, taking yours out. And if he has Luxio, one Ice Fang will also take Gabite and Gible out. Then there's his Grovyle, with Leaf Storm.
Isn't it a little odd how almost every Gym Leader is on this list? No, not really.