That One Boss: Super Mario Bros.

aka: Mario
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    Platformers 
  • Super Mario Bros. 2 has Fryguy, the flaming entity fought in World 4. At first, it seems like you simply have to hit it with the mushrooms three times, and technically that's the idea. After that, however, it splits into four living fireballs that hop here and there, trying to hurt you. And the more fireballs you kill, the faster the remaining ones will move. Granted, it's possible to kill them all in one hit, but good luck with the timing. To make matters worse, the game has a glitch where if you touch the last fireball before it dies, the door to the next world might not appear. You can escape having to reset by using a code that kills you, but that just means you have to try and beat this boss from the beginning.
  • Wendy O. Koopa. In Super Mario Bros. 3, the female Koopaling is the worst. While the others' attacks will fly offscreen, the rings of energy she fires will bounce round the room endlessly, as she continues to add more. If you can't stop her before there are more than three or so, you're not going to. Give Wendy a shot in New Super Mario Bros. Wii too. Essentially the exact same fight, but underwater.
  • Yoshi's Island:
    • Hookbill the Koopa from level 4-8 in the original game. Easy like everything when you play it normally. But when you want the 100 Points, you're not allowed to take damage even once. And this boss has really bad attacks, heavy collision damage, and you have to wait 30 seconds when you get damaged. Prepare yourself to repeat this boss over and over again for 100% completion.
    • In Yoshi's Island DS, when trying to get a perfect 100, more than a few bosses are this way. Contenders are level 2-8's Big Bungee Piranha (tentacles and continuous rain of projectiles); level 3-4's Bessie Bass; level 5-4's Moltz, the Very Goonie; and, unsurprisingly, the three-stage final boss.
  • Super Mario Sunshine:
    • Phantamanta in Sirena Beach is a giant manta ray that leaves behind electric goo and divides every time you hit him. And the order of division is up to six, meaning that you'll ultimately have to deal with 64 little mantas to vanquish. Even worse, when only the smallest ones remain, they turn pink and actively chase you. And when going to refill FLUDD, you'll find some of the water pools are electrically charged.
    • Cleaning Eely-Mouth's teeth is annoying, as you're underwater with HORRIBLE controls, and you have to be dead on when firing at his teeth to clean them. Also your life is slowly going down, and it's not obvious that you can use the bubbles to regain your health until it happens by fluke, and it takes a looong time to get low enough to hit him properly. Even if it is dead on, you have to be low enough for the water to hit his teeth to actually count.
  • Although most of the bosses of Super Paper Mario are relative pushovers (especially when compared to some other examples in the RPG predecessors of the series), Mimi can give people a major headache the second time you fight her in Sammer's Kingdom. In order to attack her you need to knock out her ruby shield (and then hit her) by launching her attacks back at her. The problem is this shield can regenerate and Mimi moves all over the stage very quickly. She's even worse the third time you fight her: First, she crawls on the ceiling and spits out Rupees. You need to pick one up and hit her with it from below, then jump on her. Easy enough, right? Well, this process has to be repeated eight times. You have a very small frame of time in which you can jump on her, and if you don't do it in time, then she starts throwing the Rupees, which are much harder to dodge. Though you can hit her while she's doing this, it's a lot tougher to do, and defending will be your highest priority. Each gem does 4 damage per hit, which really adds up. Even if you're good at avoiding damage, it's a very time-consuming fight that will likely leave you wondering just when she's gonna die.
  • Super Mario Galaxy:
    • Bouldergeist. While seemingly easy he has attacks that block your paths, regenerating body parts, shoots rocks at you constantly, and the only means to destroy it is to use stuff he throws at you that explodes if hit or held too long. If that isn't enough, he also takes over twice as many hits as any other boss in the game besides the final one (namely eight hits, while the final boss only takes six, Bowser Jr. and Kingfin five, the two Piranhas four and all others just three). His only saving grace is that occasionally he shoots golden rocks with coins at you, but that does little to comfort players looking for 100% Completion who have to undertake a no damage run on him. When the Daredevil Comet comes into play, those golden rocks that he throws at you vanish, making him the hardest boss in the game.
    • Major Burrows also qualifies. He starts off easy, but once he Turns Red later on in the fight, he'll start charging at you with blinding speeds, requiring you to ground pound TWICE before he rams into you. Also, have fun chasing him down when the dirt trails he leaves behind get in your way.
    • Fiery Dino Piranha. Not only do you have to time your spin attacks perfectly when his tail is not on fire, but he's much faster than Dino Piranha, making it that much harder to catch up to him. Also, he pulls these 180-degree turns that can cause you to run right into him just as you're about to hit his tail. He only puts out his fire when he slows down, and if he sees you trying to sneak up on him, he'll reignite, pull a 180, and start chasing you again. When he has one hit left, he never slows down, although his fire still flickers on and off. In fact, "flicker" is the perfect word: at this point, you barely have any window to attack his tail. When his tail is on fire, it leaves a freaking fire trail behind. And not a straight line, oh no, the trail follows the... smashy ball thing on his tail, so it curves everywhere. And then, at 1 HP, he starts spitting fireballs all over the place.
    • There's also Undergrunt Gunner. He appears in three different galaxies, though in two of them he's pretty easy. In the Toy Time Galaxy though, he's surrounded by flamethrowers and a Bottomless Pit, and shoots balls of electricity instead of harmless bubbles. This wouldn't be so bad if it weren't for the fact that his turret is now much taller and you have to boing around in a Spring Coil and use that to reach him, while dodging his electric bolts and flamethrowers. And if you get hit, you lose the spring coil and have to go and get it again, which can be very tricky since it's located on a narrow platform sticking out of the main arena, which means you're unable to dodge sideways to avoid the barrage of electric bolts coming at you. To top it all off, once he Turns Red he starts surrounding himself with electricity every few seconds, zapping you if you touch him.
  • Super Mario Galaxy 2:
    • Fiery Gobblegut is like Fiery Dino Piranha on steroids. He's annoying enough in his regular form (despite his glaringly obvious weak points), but his fire version takes it to the extreme. You can't touch his body without taking damage, making it very hard to take out his belly bulges during the short window you have open to you, and whenever he dive bombs the planet, he leaves lava pools. After the first three hits, he goes berserk, and it starts raining meteors. Thank God for the Cosmic Guide.
    • Also from Super Mario Galaxy 2, Squizzard. Fought in the middle of a sand whirlpool that constantly sucks you towards him unless you're standing on one of many tiny rock platforms. Throws giant rocks (and after you damage him once, spiky eggs) at you, which STAY THERE after they land until you destroy them. His weak point is his mouth, which he opens for half a second BEFORE throwing his last projectile (so by the time you've dodged it, he's closed his mouth again - you have to shoot at him and THEN dodge). You can only damage him using the (temporary) Fire Flower powerup, and you have to hit him five times (in quick succession, or he'll close his mouth and you'll have to start again) in order for one damage point to register on him. And when he's down to one damage point left, he gets these turret things on either side of him, that shoot spiky eggs at you EVEN WHILE HE'S STUNNED. And the eggs get in the way of your fireballs. But worst of all, he starts throwing massive bombs at you. And you have to do a perfect run on him if you want 100% Completion.
    • Both Bouldergeist and Fiery Dino Piranha return in the Bonus Dungeon of Galaxy 2, along with three other bosses. You have to fight the two with no checkpoints in between, but thankfully the checkpoint is before Bouldegeist. Then the Speedy Comet comes and you have to do all five bosses in five minutes and the checkpoint disappears. Bouldergeist and Fiery Dino Piranha become Marathon Bosses for such little time.
  • Ludwig in New Super Mario Bros. 2, especially in Coin Rush. For starters, the stage you fight him in (5-Castle) drains your time as you are forced to ride through most of it on slow moving fences; not even the super leaf can let you bypass these. He himself fights by jumping on chains and firing beams from them, and you have to hit him by launching yourself out of a cannon to knock him off. For the first and second phrases it's simple enough, but in the third phrase he swings around on the chain he's grabbing onto, requiring near-perfect timing to hit him. Also, time does not pause when you're entering and in the cannon, meaning that he is still moving just before you fire, so you can't rely on entering just as he swings over the cannon you're by. Again, put this in Coin Rush and by the time you start the battle you have to do all of this in only a minute, and that's if you downright burn through the level without collecting the coins.
  • Want to fight the bosses of New Super Mario Bros. U without hitting them immediately after they get up? Iggy and Roy become a nightmare. Iggy will walk onto the ceiling and use magic to create Magmaarghs. After dodging them, you have to run next to the floor where Iggy is and wait for him to fall, then immediately attack. Then, Roy has a double sided Bullet Bill cannon and jumps between floating, moving platforms.
  • Super Mario 3D World:
    • The first time Motley Bossblob is introduced in the game is not too difficult to beat it. But then comes his rematch near the end of the game, where he's capable of creating energy shockwaves whenever he tries to stomp its opponents, making it very easy for the player to get hit and/or lose the aiding clones created by the Double Cherry. The boss's increased speed while jumping doesn't help at all.
    • Fought separately, Hisstocrat and Queen Hisstocrat are bearable bosses (and, in the opinion of the fans, very enjoyable to fight). But that changes in the Boss Rush level in World Flower, because you'll have to deal with both of them in a Dual Boss fight. Them commanding the raining fireballs and the summon of snakes at the same time makes the battle more complex as well as longer (and you still have to deal with the other bosses present, including Motley Bossblob which once again rises in difficulty, in a time limit of only 500 seconds). The only easy way to deal with them is by hitting them at the same time in every opportunity, but that requires precise maneuverability with the moves of the Cat powerup. Another trick is jumping off the lower levelled plates (which does not require the cat suit).

    RPGs 
  • Super Mario RPG: The Legend of the Seven Stars:
    • The most notable one is Bundt, a cake that comes to life and attacks you for no reason. It straddles the line between either ridiculously easy or extraordinarily hard to kill, with very little space in between, depending on your characters' level (and more specifically, their defensive stat). Unlike all other bosses, Bundt has no HP - you have to knock out all of its 5 candles and then hit with a single attack. One attack from you knocks out one candle regardless of attack power, and one attack from Bundt restores one candle. You have three characters, and the cake has two parts, though only one of them lights a candle each turn. If you can manage having everyone in your party attack each round, the fight will be over in 4 rounds or less (well, the first part of the fight, but after that the more conventional second part is a pushover). Of course, that means you have to be able to tank 4 consecutive rounds of pretty hefty magic without healing once, so...
    • The Axem Rangers are plenty tough, considering there are five of them, and each one has a different variety of attacks - Red and Yellow hand out massive physical damage, Black counterattacks everything, Pink heals, and Green blasts you with powerful magic spells note  And even after beating all of them, they "combine" with their Zord/warship thing for one more go, using the insanely powerful Breaker Beam attack, which does about 70-90% of your character's maximum health.
    • Yaridovich completely counts for this, as right after you get the star from the Sunken Ship and return to Seaside Town, he takes it and you have to beat him to get it back. So how tough is he? His health and attack are both extremely high for that point in the game, he has powerful magic attacks that like Water Blast which hit your entire party For Massive Damage, and he can also put negative statuses on your characters for good measure. If that's not enough, he can also duplicate and use his moves twice in a row, and only the real Yaridovich takes actual damage until he decides to heal himself. When the duplicate is eventually destroyed, he can bring it back and make the fun start all over again. This is a sign that the game isn't messing around anymore, and that constantly attacking over and over again isn't going to win every battle.
    • Bowyer, the second boss, mainly because he can shut off one of your attack, magic, or item commands for several turns. While you do get a new party member for this fight, he's capable of shutting of your attack ability forcing you drain your limited magic points to zero, while he continues to attack you with powerful magic that hits your entire party and keeping your attack ability locked, leaving you helpless. Then, when you're low in health and magic points and need to use your items to recover, he'll switch on your attack ability and seal your item ability, which prevents you from healing, and forces you to continue fighting him while you're exhausted. He can alternatively seal your special ability, causing the fight to become a long battle of attrition as your magic is sealed, limiting you to normal attacks while he can still rain destruction upon you.
    • Valentina has more HP than anything else you've fought at that point in the game, and the list of magic spells she has access to is insane. In fact, she uses more magic attacks than any other boss in the game, many of which are also That One Attack, such as the infamous Water Blast, Petal Blast (turns your entire party into Mushrooms), and Aurora Flash (can put your party members to sleep). The battle also starts in an unconventional note in that Dodo, Valentina's flunky, will whisk your middle member away immediately after the battle starts to engage in a Duel Boss. It is universally recommended for this party member to be Bowser, as he's the only one sturdy enough to withstand Dodo's attacks, and also strong enough to defeat him quickly. However, it'll take a while for him to rejoin the fight with Valentina, leaving you one party member short for a few turns. And Dodo will also return and still have some fight left in him, giving you two headaches to deal with.
  • Paper Mario:
    • Original Paper Mario:
      • Huff 'N Puff is a giant cloud, and every time you hurt him with your jump or hammer, tiny little cloud baddies will pop out of him. If you didn't get rid of the tiny clouds by his next turn, he would swallow them up and heal himself. Often there were six or seven tiny clouds that couldn't all be removed by the next turn. Also, he had a devastating electric attack, and often charged himself up so it would shock you if you jumped on him. Truly one of the more irritating bosses in the game.
      • The Crystal King is no slouch. He doesn't really rely on one gimmick, either; he has a powerful healing move that can undo multiple turns worth of damage (which he can spam), he can split into copies, and his attacks really hurt (one can even freeze, taking Mario out for 2 turns at a time).
      • The Lava Piranha has two forms, making it twice as hard to beat. Its first form can hit reliably hard, and takes a while to kill. One you kill it, the battle seemingly ends until the thing bursts out of the floor again. Now, it's gotten a significant power boost, even more HP, and is on fire, making contact attacks impossible. Unless you use Sushie's Ultra-Rank attack, in which case the second part of the fight becomes much, much easier.
      • Jr. Troopa can get quite tough in later fights, mostly by changing his attack styles radically. Some of his forms include growing bat wings and a spike on his head, making him immune to conventional hammer and jump attacks, and getting a magic wand, which lets him hit tremendously hard.
    • Paper Mario: The Thousand-Year Door:
      • The Bowser and Kammy fight, which can be ridiculous if you are unprepared for it. Basically you have to go through Grodus (a normally tough fight on his own), followed immediately after -- with no gameplay break and no chance to heal or save — by Bowser and Kammy, who can each hit hard and, thanks to Kammy's presence, heal. Have your Star Points in or around the 90s so that when you beat Grodus, the Level Up makes sure you're in tip-top shape for the next battle.
      • Cortez is often considered one of the harder bosses. His health seems low at first... until you realize that he has three forms AND gets a free health refill in the third form, meaning you have to deplete his health bar four times over. His first form is easy, but his second form has a nasty charged attack that can take out large chunks of valuable health. This pales in comparison to his last, and longest, form where he hides behind his four floating swords which all attack you at once, meaning he can land five attacks in one turn if you aren't careful.By the way, the floating weapons all count as spiked enemies AND flying enemies. This means none of your partners can deal damage to them without special moves, and only three of them can damage Cortez while the weapons remain (Mario's hammer doesn't work either). So you had better pray to God that you have Spike Guard (allows Mario to jump on Spiked enemies) equipped or you're screwed. Oh, and one of the weapons can poison you and almost all of them have fairly tricky timing for their attacks that makes dodging and preventing against that poisoning difficult (due to the relatively low amount of HP you get in this game, poisoning is a very serious problem).
      • Gloomtail in The Very Definitely Final Dungeon is a real nasty thing that you'd only know about in passing if you bothered to listen to the storyteller, as otherwise the encounter with this beast is a shocker. This battle doesn't have any special gimmick to it, he just hits real hard. This guy has a lot of HP, has several, very powerful attacks and good defensive power. Several of his attacks (particularly his earthquake), are very difficult to dodge, and Goombella outright tells you to use Vivian's Veil to completely avoid his MegaBreath, which is extremely powerful. Your HP will constantly plummet troughout the fight, so players shouldn't be shocked if they end up using half their inventory healing all the damage this guy does.
      • The Final Boss, the Shadow Queen, is also particularly nasty. Excluding the Bonus Boss, it has the highest HP count of the game (150. For the record, neither of the previous bosses ever broke 80 HP), it has flunkies in the form of its hands, which possess an extremely annoying and difficult to guard attack that drains your HP for the boss, it can inflict various status effects (including poison and infatuation), it can boost itself for a while and it can get as many as 3 attacks in per turn because of its hands. The hands themselves have low HP, but they'll just keep reviving every turn if you keep killing them, which is practically mandatory as the boss hits hard enough on its own. This results in a long and arduous fight in which you play the role of the healer that ocassionally pitches in while you support a Partner with multi-targetting attacks (preferably Vivian for her Fiery Jinx).
    • Paper Mario: Sticker Star:
      • If Megasparkle Goomba put up the points that you need to use the Battle Spinner and a boss's weakness to fight effectively, Tower Power Pokey hammers in these points with a sledgehammer. You thought Megasparkle Goomba's 90 HP was crushing? Try 300. With sky-high defense to boot (7, in a series where any defense score is notable). Firstly, each turn after the first he can't be hit by hammers. Then, after he's fully emerged from the ground, he'll summon green Pokey flunkies (and do it again occaisonally). His spinning attack is hard to block completely, and his falling attack has a chance of crumpling you (essentially complete paralysis) for multiple turns if not blocked. And he can heal himself for 10 HP at a time if he so desires. You essentially can't defeat him without using his weakness; even then he's a tough fight. And the bosses get harder yet.
      • The final boss, Bowser, is a horrid Difficulty Spike from the previous boss(es), and that's saying something compared to the standards for boss fights in this game. He has an absurb amount of HP, insane defense, and a whopping five phases. He's spiked, so if you favor jumping stickers, better learn how to time your hits with the hammer or you'll have to buy a lot of Super Boots. All of his regular attacks take off 10 HP unguarded, and his jump attack can crumple. You will not beat him without having an entire inventory full of high-power stickers and frequently use the Battle Roulette with pinpoint accuracy. Even if you do, you'll have to take along the Thing Stickers that will weaken him, or you won't last beyond the first phase. Even then, each phase drags on forever, and you'll never know when the next one will start.
        The first phase summons three flunkies. Because of the choice of flunkies, very few stickers will take out all three at once. On top of that, whenever one's killed, even more are summoned. The second phase has a giant Thwomp. Whenever it's up, Bowser will take only 1 damage from anything. It also hits twice for 10 damage, on top of Bowser's barrage of attacks. On top of that, only one kind of sticker will knock it over and make it vulnerable to Thing Stickers. The third phase, Bowser uses only one attack, but it's a doozy. He summons a barrage of fireballs which are impossible to block completely. Using the proper Thing Sticker won't work permanently. The fourth phase can be ended in one move, but if you can't, you'll have to deal with an invincible enemy in front of Bowser. The final phase? Hopeless Boss Fight, yes, but his attacks hit for horrendous amounts of damage. The third move is a devastating combo that will crumple you for 3 turns if you get hit with the final blow, at which point you can just shut off the 3DS. Oh yeah, and his fire attacks can destroy your stickers. It's like the developers wanted players to suffer in this game.
  • Mario & Luigi:
    • Mario & Luigi: Superstar Saga:
      • Piranha Mom, who is not only tough herself, but spawns two smaller piranhas. Which wouldn't be so bad, except the only way to win the battle is to attack Mom directly, whereupon the two smaller plants both spit fire/lightning at both Mario and Luigi. There's no real way to predict which brother is going to be attacked by which plant, unlike every other enemy in the game up to that point, and the attacks seem to vary timing to make them hard to dodge. Mom regenerates health, and creates new Piranhas any time the old ones die.
      • Trunkle. The thing has crazy defense, so that your moves which do twenty to thirty damage to normal enemies does... 3 damage, maybe 6 if you get a Lucky shot, on him. Plus every other turn, he'll inhale enemies to heal himself, and do damage to you if you don't jump properly. Eventually he breaks apart, but that's not the end of it - he's now four tiny Trunkles, and if you don't guess which one is the real Trunkle and defeat it first, he reforms and you have to start all over again! Attacking the tree on top of his head does shorten the battle, but it causes Trunkle's defense to skyrocket.
      • The Bean Piranha. It has a very low HP count for a boss, but it more than makes up for it by the fact that it has insanely high defense (like plenty of bosses do in the late game). This is because you're facing it on solo with Luigi, who is the slower and offensively weaker of the two bros. Trying to take it out with anything other than Thunder is suicidal. Getting hit once by this guy probably means you'll have to waster your precious turn to heal, and unless you smart up and spot the differences between the two versions of his attack, you'll probably get hit again and have to waste another turn to heal. This fight can feel like a Marathon Boss simply becaue of how slow progress is made, and it doesn't help the fight comes out of nowhere.
    • Mario & Luigi: Partners in Time is generally rather easy for a Mario & Luigi game, but two bosses stand out for their difficulty.
    • The Final Boss. A) it is Nightmare Fuel incarnate for Mario's target audience; B) it is comprised of seven different targets—though thankfully you only need to attack three of them; C) it, unfortunately, has incredibly high defense for those three targets you need to hit; D) those three targets need to be attacked in order, otherwise you won't make any progress; E) only the final target's HP counts, the previous two need to be disabled just to expose the weak point, and they can and probably will revive; F) it has powerful attacks that can take down one pair of Mario Bros. with ease; and G) it comes after two other bosses, who—thanks to their high HP and powerful attack—can easily make you use up a lot of your healing and Bros. items. An even-leveled player can easily spend upwards of twenty minutes to half an hour on this final battle. An underleveled player... well, let's just say it balloons into full-blown Marathon Boss territory.
      • The Elder Shrooboid is easy in its first phase; then it grows and summons a flying saucer with a countdown. If this countdown reaches zero then game over. Resetting it requires hitting the boss's spike ball attack at the saucer. Mario and Luigi also hit the ball in different directions. Hope you hit it with the right brother. Finally the Shooboid's other attacks have increased power.
    • Mario & Luigi: Bowser's Inside Story:
      • Dark Bowser and Dark Fawful Bug. Now, neither is difficult to dodge attack wise, not particularly hard to damage, but they take forever to kill. First it's Bowser vs Dark Bowser, then at 1000 damage he heals, throws a whole bunch of enemies, you have to dodge pretty much all of them and said boss himself to reach him, then hit his stomach, then suck up the Fawful Bug... and Mario and Luigi THEN get their turn. The bug thing itself has three legs, two glasses and the Dark Star as targets, so Mario and Luigi have to destroy all the legs and the glasses to reach the star... get about two turns of attacks against it, then it repeats from the first Bowser phase.
      • One of the toughest bosses for Mario and Luigi is midway through the game when you reach Bowser's brain and fight copies of yourselves called Memory M and Memory L and yes, they are hard. Remember in the old days how cool it felt to grow to Super Mario or Luigi, or to get a Super Star and become invincible and run through your enemies for massive damage? Well that's about to bite you in the rear pretty hard when these guys do it to you constantly through the fight, which means if you're not good at perfectly dodging or countering attacks at this point, you're pretty much screwed. Also for more fun, their stats are similar to yours, meaning that Memory M is offensive with more speed and Memory L is defensive with more health. Memory L also doubles as the medic, so if you knock out Memory M, he will just revive his fallen brother. Naturally, you would think to defeat Memory L first to prevent him from recovering his brother, but that's easier said than done since he's based off of Luigi, who hates to fight, he will often run off of the screen until his brother faints and remaining completely invulnerable until he returns to the battle. This fight is usually the most remembered in the entire game, not just because of a nostalgia factor, but also because of how difficult it is.
      • The Junker. It seems like a standard Flunky Boss, but then he sucks Luigi up and sticks him inside one of the Junker Cans. While Luigi is in the can, you have to keep track of which can holds him and destroy it. All the while, the Junker and the cans are hitting you with powerful attacks, as well as the cans frequently swapping Luigi around. Also, the cans have at least three turns worth of HP, and if Mario goes down, the battle ends. Also, by the time you finally get Luigi out, he's almost guaranteed to do it again. Did I mention that's one of the few attacks in the game that's completely unavoidable?
      • The Fawful Express. It's only attackable with the flame attack, has a semi turn timer you need to defeat it in, the mountain halfway through also becomes a giant mech and there are at least four different attacks to dodge. Since the flame attack is controlled by the DS microphone, it can be difficult to get full damage on your attacks, and the train likes to heal while it's in the mecha. Also, since the flame attack involves blowing into the microphone as hard as possible, you're going to end up pretty darn lightheaded which makes focusing harder.
      • Every boss can feel like this (some more than others), along with Marathon Boss, if you're going for a Challenge Medal run. The Challenge Medal is an optional equipment piece that highly increases every enemy's stats, but increases the coin prize at the end of each battle by 1.5. Combined with a low-level run (in order to get the Easter Egg at the end for doing so), this can take already hard bosses' difficulty to ridiculous levels, also making Gauntlet battles outright Unwinnable because of their turn limit. Note that the Medal also affects Bowser, who has it worse because he's on his own. Using the Medal, unless you're an expert at dodging/blocking everything (and really, you should be since you're the one who decided to go full-game with it), then you're in for quite a few moments of frustration. Enjoy the Junker.
    • Mario & Luigi: Dream Team:
      • Torkscrew has a ton of HP for the point in the game you fight him, and he has several attacks which are long and drawn out. Jump at just the wrong time during his digging attack and you'll have to chase him down for half a minute while steadily losing coins and jumping over mines. He's also got a spinning drop which is hard to counter, does terrifying amounts of damage (say, 40, when Luigi's HP may not be above 70), and has a good chance of lowering defense; if Mario is hit, he won't survive much longer. And he will sometimes chase one bro into the background, which forces the player to multitask because enemies will attack the other, in addition to Torkscrew himself. If that wasn't all, he can't be jumped on. This is only the third area's real-world boss, by the way.
      • Thunder Sass might count for this title. His attacks hit very fast and hard and can cause dizziness (which stops you from doing anything, and since this is the dream world, where you have one character, you don't get a turn plus his next attack is guaranteed to hit), plus his minions make it harder to avoid an attack too. Think you can spam your powerful attacks to kill him? Nope, because the gimmick of this fight is you are not allowed to use any sort of attack (including items that affect enemies) and must counter his attacks to hurt him at all. You can't even use badge effects to heal yourself without using items, which is a real pain in Hard Mode since you're only allowed 10 of each item. And the kicker? This is pretty much a miniboss, as you need to beat him to fight Big Massif, which is another That One Boss (see below). That's just cruel.
      • Heavy Zest, another miniboss you need to beat to reach Big Massif, is another pain. Not only does he hit very fast and hard, like Thunder Sass, but the tells for the attack where he rushes off stage and charges into you are very hard to figure out. But that's not what makes him difficult. No, it's the fact that there is a turn limit on this fight. You get three turns. And it doesn't end when you beat him. No, you have to defeat his minions as well. Hope you've figured out the Luiginary Attacks by now.
      • There's Big Massif, who gets an attack boost whenever you kill his minions. Problem? Due to the Dream World's mechanics, all of your attacks, regular or Luiginary, are going to at least hit some of them. And don't think you can fail at your attacks to prevent the attack boost because he has one attack that uses these minions and gets more powerful as their numbers increase.
      • Wiggler would normally be a tolerable fight... if Popple wasn't involved. Every now and then Popple will try to attack Wiggler, and if you don't attack him twice in the same turn with both Bros., then Wiggler's already strong attacks will hit even harder and become harder to predict. Only problem is, if you're having to use 1-Up Mushrooms to revive constantly, there's no stopping him. And even then, sometimes you can't stop him. During Wiggler's normal charging attack, on the rebound, Popple will cling to the one targeted, which gives jumping to dodge Wiggler a massive delay. For Wiggler's enraged charge attack, it's very hard to dodge and takes off giant chunks of health; and if one Bro. gets hit, then Popple will trip the other, forcing them to be hit unless they jump at precisely the right time. And guess what? After whittling down Wiggler's quite high HP, Popple attacks. With no break from the last fight. His attacks are tough to counter and the tells are short (especially when he kicks a brick block, then sucker-punches [erm, kicks] the projectile into you and does even more damage). If you miss his spinning attack, then he hits you with a deadly uncounterable attack. Expect to burn through a lot of 1-Ups, and it's oh-so enjoyable to see Wiggler chasing off Popple.
      • Earthwake, the third giant boss, who can turn into a flying hammer at one point and repeatedly strike at Luigi (which in itself is That One Attack due to how hard it is to block/counter). He can take you from literally full health to zero before you can move if he uses this attack, and on Hard Mode he uses it repeatedly.
      • Pi'illodium, the guard of the Pi'illo Temple in Somnom Woods. This boss not only has a machine gun equivalent laser attack which you somehow have to memorise the pattern of in about 10 seconds, but also one that has him fly off screen and come smashing down on a bros head, with the timing needed to dodge it being both split second and mostly blind. It can also chase after Mario and Luigi while firing a constant barrage of missiles, heal itself on a regular basis and activates a deadly self destruct timer when near to death (which can act as a Kaizo Trap).
      • Kamek in his final boss battle, since he splits into four clones, all of which have their own attacks, can heal each other and boost each other's attack stats.
      • Giant Bowser, since the battle is both a Marathon Boss filled with precision dodging and requires the gyroscope in at least two different phases (the gyroscope isn't particularly accurate at the best of times and it's used here in situations where failure is basically a One-Hit Kill).
      • Antasma (final time), since his attacks all have a chance of putting Mario to sleep, causing him to lose a turn (in the Battle Ring) and have to escape a deadly gauntlet of saw blades and pits to try and return to the fight.
      • Dream Team also has the Zeekeeper. Not so hard when the battle works, but way, way bad when you're on Hard Mode with no way of healing (outside wasting one of the two turns you actually get to attack him in) or when the motion controls in the zero gravity section fail to work altogether due to a Game-Breaking Bug. Or when you're on Hard Mode AND the motion controls fail, in which case you might as well as consider yourself cursed. Oh, and near enough three quarters of the battle is his turn. How? Because he always runs away, and you have to catch him to attack yourself. Which happens after between two and four of his own attacks, all in a row. Made worse by how you can FAIL to catch him, at which point he mocks you and flies into the dimensional rift again, giving you no chance to fight back for a while.
      • Dream Team also continues the trend of the final boss being ridiculously difficult for the game. First of all, its arms need to be incapacitated for you to being able to target its weak spot For Massive Damage. Second of all, it hits hard with all of its attacks, and they're hard to avoid. Third, it can summon enemies in amounts that is restricted to the Dream World enemies/bosses, and while the enemies are on stage, the boss retreats to the background to heal itself AND its arms. Lastly, it can summon a background enemy which takes an ungodly amount of hits/counters to finish off. Even with the best gear and the best Bros. Attacks, this boss will likely mop the floor with you. Repeatedly.

    Others 
  • Yoshi's Safari has two of these: Magikoopa and Big Boo.
    • Magikoopa teleports rapidly all over the place, thus making it very hard to hit him. As soon as he fully reappears he'll immediately fire off a magic shot that takes several shots to destroy before immediately teleporting around again, only giving you a split-second to hit him. Between defending against his shots and shooting all around trying to catch him as he reappears, expect your power meter to be very low throughout the fight.
    • As for Big Boo, what makes this fight so hard is the constant stream of debris flying toward you, and all while moving around chasing down a constantly-moving Big Boo with many invulnerability frames. After you take him down, he'll split into three smaller Boos, and you have to aim at the one with the tongue sticking out, still with the invulnerability frames and the flying debris. You'll most likely need your mushroom item for this fight.
  • Luigis Mansion:
    • Boolossus, a horrendously hard boss battle that involves freezing a bunch of tiny boos in order to defeat it. Unfortunately, as the number of boos get smaller, they become harder to hit, until it's almost nigh impossible to hit the very last boo with your freeze weapon. And they know when you are using the ice, because they run away when you do. Its almost impossible to get them unless you shoot while they dive bomb you, and when that happens its like impossible to aim before shooting.
    • Technically a mini-boss, but Sir Weston is easily the most difficult portrait ghost for the perfect run. His room is covered in ice, so it's very difficult to suck up him up in one go.
  • Luigi's Mansion: Dark Moon:
    • The first boss, because it requires more thought and variety in strategy than every other boss prior to the fourth once, so it acts as an incredibly brutal Wake-Up Call Boss. The annoying spiders don't help matters.
    • The fourth boss (Shrewd/Scornful Possessor). Not only does the battle use different gameplay mechanics than every other boss battle in the game, but you have both a limited amount of ammo and the annoyance of the boss regenerating health to boot. And if your vehicle overheats (like if the boss hits it during its one true attack) its an instant game over. And prior to this point you've never had any practice with the shooting mechanics at all. It's bad enough a significant amount of players have practically given up on the game because of it. Also, you have two ways to aim. You can either use the circle pad, or tilt the 3DS. However, the tilting control is inaccurate, so you need to use the circle pad. It might seem like it's not a problem, until you discover you can't turn off the tilting controls, so you will have to set your 3DS on a surface in case you want to use the pad.
    • The fifth world boss, Ambush Manuever. Big Boo is fought in a similar manner to Boolossus in the first game. He is composed of small Boos and has 2 attacks which, due to his humoungous size, can be quite difficult to dodge. To actually beat it, you have to wait until he uses one. If he slams the ground, he will eventually get dizzy and you need to perform a power surge on his tongue to send him in front of the train. However, more likely than not he will be in an area that doesn't have enough room to perform one (To do a power surge, you need to pull it's tongue in any direction). If it dives into the ground, it will charge into you. If it hits other parts of the train, it will simply get dizzy, giving you a free hit. If you manage to send it in FRONT of the train, it will then split up into smaller ones. (Think about an orange on a squeezer.) You then need to send every single one of the 8 Boos into cages using the same tactic from the former attack. Luckily for you, said cages are conveniently attached to the train. Also, if you send a Boo into a cage that already has one inside, it will simply bounce off it. And every attack, even from the smaller ones deal 20 damage and that the train is constantly moving. If can't get the timing right, this boss will be your nightmare.

Alternative Title(s):

Mario