Ah, yes, ''Rosenkreuzstilette''. This franchise brings so much nostalgia to those who have played the classic ''Franchise/MegaMan'' and ''Franchise/{{Castlevania}}'' games. As a tribute to the difficulty of said games, you can be sure that it has some despicably tough bosses that you'd find within the different adventures in the series. In fact, these guys and girls are the main reason why this series is NintendoHard, and why many players have been [[ThisLoserIsYou humiliated with]] [[ShoutOut several references]] to classic computer and video games on their respective stages' GameOver screens. As a rule of thumb, Grolla and Pamela's versions are harder by default with their damage output doubled and use of melee attacks that require close-up tactics. They'll be mentioned however if differences are notable enough to change the strategy of the fight.

'''NOTE''': {{Final Boss}}es and [[WakeUpCallBoss Wake-Up Call Bosses]] are not to be added unless they're overly difficult by their standards. {{Bonus Boss}}es are not allowed; they're optional and have no standards for difficulty.

* In discussions about the game, all the bosses in the Sepperin Stages are mentioned frequently, especially the [[AdvancingWallOfDoom Demon's Wall]]. This thing is similar to the Mecha Dragon from ''VideoGame/MegaMan2'', and for good reasons; you have to fight it on only a few block platforms above a [[BottomlessPits bottomless hole]], and the CreepyCoolCrosses and energy balls it shoots at you travel across the screen rather quickly, and not to mention, once they're above or below you, said energy balls can split in two and its two sections can travel both upwards ''and'' downwards. And what's worse? It shoots even more of them once it TurnsRed. And thanks to how narrow the platforms are, unless your character is standing on the opposite edge of where the attacks will hit, the knockback will kill you.
** While ostensibly its weakness, [[spoiler:Klageharnisch]] is so unwieldy and awkward of an attack that aims vertically rather than horizontally, it tends to be discarded by many players even if it [[spoiler:can kill it in four hits]].
** It gets even worse when you fight it as Grolla, due to the fact that you'd have to get up close to actually damage it with your slash attack. Since her charged slash is the only reliable attack that has the range to hit the thing, and is your weakest attack if her health is above 50%, the fight becomes all the more tediously frustrating. Compared to the one in the main game, this thing in ''Rosenkreuzstilette Grollschwert'' is a complete and utter bastard.
* The Deviled Egg, a.k.a. the Yellow Devil from the ''Mega Man'' series, appears in [[spoiler:Iris Stage II]]. Remember how hard the Yellow Devil was in the original ''Mega Man'' game? This guy's basically the same thing. The pieces of its body fly across the room so fast that they can be hard to jump over or slide under quickly. Its weak point is its eye, just like the Yellow Devil, except it opens up all over its body quite often, making it hard to hit. Oh, and what about when it turns red!? Yep, this thing has a new twist that makes it different from the Yellow Devil; once it turns red, [[GravityScrew it'll start flipping everything upside down every now and then]], and vice-versa! The flipping has the same effect as the waterfalls from before the fight; once you're flipped, [[InterfaceScrew your controls are reversed]], which means dodging its attacks is harder.
** For Tia this is mitigated [[spoiler: by the boss's weakness, Liebessturm, being a full screen attack that doesn't care where the boss's eye spawns each time it reforms.]] Grolla, [[WhenAllYouHaveIsAHammer on the other hand...]]
** Before that, there's the Webmaster Spider, who's surprisingly just as tough as the Bosspider found in the original ''VideoGame/{{Mega Man X|1}}'' and its [[VideoGameRemake remake]], ''[[VideoGame/MegaManMaverickHunterX Maverick Hunter X]]''. The difficulty of figuring out where it will stop when it crawls down as well as the short amount of time it takes to shoot its red core before it closes back up, as well as its increasing speed as it takes damage explain it all. Oh, and there are also spears on the walls on each side of its arena. [[spoiler: Additionally, its weakness, Freudenstachel, has an oscillating firing pattern that makes it difficult to line up the attack with its weak point.]]
* Freudia Neuwahl is a major jump in difficulty compared with the other seven RKS bosses.
** In the Opening Stage, she was a WarmUpBoss that had a fairly simple pattern of throwing ice shards at you that could be dodged if you stayed to one side and jumped over them, and she doesn't turn red. She makes up for it in her home stage, what with her ability to throw more snowflakes than a ''VideoGame/{{Touhou}}'' game that [[BulletHell fills a large chunk of the arena with ice]], constantly fires a wall of lasers that will have you jumping awkwardly between a narrow gap while walking away from the icicles, creates multiple ice clones that use Freudenstachel (what's basically an ice machinegun) that can have you wasting time attacking them as they're hard to distinguish between the original and don't take any damage, and worst of all, her weakness weapon only knocks off ''half'' of her HP before draining completely. After that, you'll have to do the rest yourself. Assuming, of course, you didn't use it on the Quick Man [[OneHitKill death]] [[FrickinLaserBeams beams]] earlier in her stage. To put that in perspective, her intro stage as mentioned has no changes in her pattern. You know the gloves are off when [[ThisIsGonnaSuck her healthbar is completely red]]. Did we mention her stage itself is also ThatOneLevel thanks to said death beams?
** Freudia becomes harder in the rematch at [[spoiler:Iris Stage III]], for solely one reason: The arena the fight takes place at. Dodging her more dangerous attacks was somewhat easier because her boss stage was the most spacious out of all other bosses. The rematch stage feels cramped in comparison, her two most dangerous moves taking up the whole screen, leaving little to no room to dodge.
* Even if she's not about as tough as Freudia, there's no doubt that Grolla herself, as a boss, is still quite hard. Her unpredictable movements, as well as her fast tackle attack, can take off your health much quicker than you can say "plot device". And that's not all; her [[BeamSpam multi-cross-cut laser-like slash attack]] comes out fast and hard to avoid. Oh, and even if you use her weakness weapon, [[spoiler:Trauare Wrede's Klageharnisch]], she still isn't easy. It's also notable that both Freudia and Grolla are the only two bosses that aren't weak against their own weapon in the first game.
* As Spiritia, avoiding Trauare Wrede's attacks requires precise timing if you want to avoid getting hit by her Leviathan lunge and Klageharnisch. If she hits you with Leviathan, you'll likely lose one-third of your HP in a single hit! It doesn't stop there; once she turns red, she'll unleash her DoppelgangerAttack to follow her during her lunging attacks, making this fight require some cat-like reflexes to dodge Trauare, slide under her first doppelgänger and almost immediately jump over the second. [[FromBadToWorse Worse still]], should you be too far away from her from her initial lunging attack, [[TheComputerIsACheatingBastard she WILL double back and lunge at you again, while her doppelgängers follow suit to make sure she hits you]]! Even worse still, If a player is unfortunate enough to gain too much distance from Trauare after dodging her attempt to thrust her Leviathan into you again, she can repeat this attack ad infinitum until she does. However, she's much easier if you take the low route in her stage. If you fight her there, the arena will be filled with water, giving you much more leeway in your jumps, and all you really have to worry about is not jumping too high into the spikes on the ceiling. The rematch in the penultimate stage doesn't have this luxury, however.
* Since you're playing as Grolla in the alternate mode, Spiritia takes her place as the graveyard stage boss in ''Rosenkreuzstilette Grollschwert''. At first, she's not all that bad, (she'll just fire the occasional charged shot and send Lilly after you, which is easily tellegraphed thanks to the sound cue), but when she turns red, she becomes much worse than Grolla herself was as a boss. For starters, Lilly will give her a Cross-Tank to refill her HP, her Freudenstachel attack becomes annoying as hell when you're on the ground, and she can also aim her Lustatem at you if you're climbing the walls of the area, which can also be annoying. And if you think that's bad enough, when she gets close to you, she'll call forth her charged Klageharnisch attack. [[spoiler:Since Klageharnisch was Grolla's weakness weapon in the main game,]] the resulting blast from her charged Klageharnisch may even kill you instantly! More generally, she avoids what made Zero an AntiClimaxBoss in ''VideoGame/MegaManX5'' by constantly dashing and firing strong attacks, which as Grolla are legitimately a problem as she takes double damage that makes up for her slower speed and more obvious signs of attack. It's as if the creator wanted to fix everything that made X pathetic as a boss with this fight.
* The first phase of the fight against [[TheGrimReaper Raimund Seyfarth]] pits you against his fast-flying scythe, Grassense. Grassense can be a pain because it flies around so fast, and in addition, several smaller scythes can also come flying at you really fast, which reminds players of how tough Death himself was in the ''Franchise/{{Castlevania}}'' games (particularly to [[VideoGame/CastlevaniaI the original 1986 game]] and ''[[VideoGame/CastlevaniaRondoOfBlood Rondo of Blood]]''). Once you've done enough damage to Grassense that Raimund himself will turn red and face you head-on, the rest of the fight isn't too tough, unless you go ballistic and try to attack him when he's not doing his Grollschwert rain attack only for him to counter your attack with his own laser slash attack, of course.
** In the hands of a skilled player, his counter-attack in his second phase can be used as an AIBreaker. However, really only works for Spiritia and the trick to exploiting his counter-attack will require some practice to develop a rhythm to avoid getting hit (or take little damage as possible).

[[AC:''Rosenkreuzstilette Freudenstachel'']]
* In the C75 and C76 trial versions of ''Rosenkreuzstilette Freudenstachel'', Grolla has easily proved to be the toughest boss in said demos, even tougher than she already was in the first game. She throws even more {{Sword Beam}}s when she TurnsRed than she did in the first game, and even more during her multi-cross-cut laser-like slash attack, in addition to being able to climb walls and attack you from above. And worst of all, the ground is slippery from the bloody rainstorm just like the last two rooms before her.
** And she's still pretty tough in the full version, and rightfully so. Just as you enter the boss room, she surprises you with a fast and long leap to the top of the wall you came in from and comes down to pull off her SwordPlant attack, which can catch you off guard if you're not careful. She is fast and her attacks are hard to dodge, even if her new multi-cross-cut laser-like slash attacks are now predictable.
* In the full version of ''Rosenkreuzstilette Freudenstachel'', we have Schirach Fühler. Every time she jumps and lands on the ground, she causes an earthquake, which wouldn't be so bad, except she does it ''all the freaking time''. And sometimes she creates earthquakes simply by standing and striking the ground with her hammer. And if you're ever stunned by an earthquake, she will grab you and send you flying with a painful MegatonPunch. Her other gimmicks include falling rocks and hurling ''huge'' boulders that are difficult to avoid. Worst of all, her weakness, [[spoiler:Freudenzwinger]], can be somewhat tricky to land, as it ends the moment Freudia gets hit, and you only have limited weapon energy.
* Dolis Warmind can be pretty tough as well. Seeing that Freudia, who was previously the hardest of the RKS bosses in the first game, is now playable, it's rather fitting that Dolis take said position in ''Rosenkreuzstilette Freudenstachel''. Dolis is fast and unpredictable and loves to surprise players with hard-to-dodge attacks and leave them not knowing where she'll strike next, which makes her a pain in the ass to take down. Not to mention, her Fesselspirale attacks are pretty fast as well.
* As with the Deviled Egg back in the first game, Devil fights are never fun, not unlike those in the ''Mega Man'' games, and the Dark Devil, [[spoiler:the OneWingedAngel form of Eifer]], is definitely no exception. Remember how the Shadow Devil functioned in ''VideoGame/MegaManX5''? This beast acts the same way, even if it's not as bad as the Deviled Egg was. However, once it turns red, it gains a new attack that creates a wind that slowly pushes you along the floor as its body pieces fly across the screen à la Deviled Egg, which can make them tough to avoid. And if you think this thing is tough enough for Freudia, wait until you fight it as Pamela, because this thing can be a ''NIGHTMARE'' for her.
* Speaking of Pamela, she as a boss in the main game has a pretty intense fight of her own, which is basically what Grolla aspires to be. She's insanely fast, and her attacks can easily catch you off guard. She jumps and [[TeleportSpam teleports]] around a lot during the battle, making her hard to hit. Her fire dash attack is fast as well, and she gets even worse when she turns red. The fact that her weakness weapon, [[spoiler:Weißteufel, doesn't slow her down]] doesn't help, either.
* Zorne [[TookALevelInBadass took a serious level in badassery]] in this game. She went from a fairly linear boss who threw bombs that were easy to dodge if knowing the right timing to it, to an ungodly fast bomb-throwing CuteBruiser who jumps around the walls either to strike with her gauntlet, or to jump over the player to throw bombs that now explode upon contact with each other should another bomb be thrown, which happens frequently, making her attacks fairly unpredictable. While not as hard as most examples mentioned in this page, Zorne certainly becomes a trickier boss compared to the first game.
* Even by final boss standards, the two-phase boss in the final [[spoiler:Iris]] stage is considered ''ABSOLUTELY RIDICULOUS'', so much so that it's not even funny. [[spoiler:First up, you have to face a BrainwashedAndCrazy Spiritia, who outshines even Iris herself in terms of difficulty, as dodging her attacks requires fast reflexes, split-second timing, a lot of patience, and a quick eye. Her attacks come out fairly fast, and most of them are hard to predict, meaning you'd have to react just as quickly in order to avoid them quickly. Perhaps her most infamous attack has her raining swords upon your head and then turning them into lightning bolts at the same time that she slides at you. After her, you face Iris herself, in her Wings of Madness form, whose attacks are just as fast and hard to dodge, and also require fast reflexes to avoid. More energy balls would come down and split into two more that quickly travel across the floor after the homing ones beforehand zoom in on you. Iris' larger homing energy balls would also require fast reflexes and plenty of patience to avoid completely, and lots of them would home in on you one at a time. Her multi-Blitzstrahl attack follows you one lightning bolt at a time, and Iris herself finishes up the attack with a whole line of lightning bolts that takes up much of the screen, and you would have to be on either edge of the screen to avoid this screen-filling technique completely. And to top it all off, this is just about the only boss fight where the boss itself has an extended health bar. Oh, and if you think that's tough enough with Freudia, just wait until you get to this boss as Pamela.]] Have fun!