A long-running series like ''VideoGame/SuperRobotWars'' has, of course, featured some difficult bosses over the years.

'''NOTE:''' FinalBoss and WakeUpCallBoss cannot be ThatOneBoss without being overly hard by ''their'' standards. Please do not nonchalantly add them as examples. {{Superboss}} is completely banned, as they're supposed to be an overly challenging boss.

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* ''VideoGame/SuperRobotWarsAdvance''
** [[Anime/MobileFighterGGundam Master Asia]] is a tough opponent to hit at the best of times, has two separate HitPoint bars thanks to his mount Fuunsaiki, and in his final encounter will be RegeneratingHealth infinitely unless players knock him down from approximately half his {{Hit Point}}s to zero in a single attack. Without an allied character with the Spirit Command "Valor"[[note]]Deal twice the amount of damage on your next attack[[/note]], it's definitely one of those easier-said-than-done things. There's a reason he's called ''[[RedBaron The Undefeated of the East]]''. The first encounter with him is especially notable as he's the first opponent in the game to possess a strong [[AreaOfEffect MAP Attack]] and he uses it at every opportunity. He's significantly easier in the Platform/PlayStationPortable VideoGameRemake due to the changes to the weapon upgrade system that makes it likely for players to have access to more powerful finishers, but is still extremely deadly if players aren't properly prepared.
** Unlike most instances of ThatOneBoss in this franchise, [[Anime/{{Daitarn 3}} Don Zauser]] doesn't deal any nasty StatusEffects from his attacks, no damage-reducing barriers or unit abilities such as "Afterimage"[[note]]Gain a 50% chance of evading any attack[[/note]], the scenario he's in doesn't have a turn limit, nor does he possess a MAP Attack to allow him to threaten a player's units at once. What he does have have is bigger, badder numbers than anything else in the game: boatloads of HP, offset with incredibly high accuracy and evasion stats (moreso than the FinalBoss), and coupled with very high damage for his attacks, Don Zauser will simply overwhelm players through sheer force; there's practically nothing one can do to mitigate his advantages. Unless players have made sure to upgrade only the units that appear after a particular route split, and are extremely frugal with their resources throughout the MarathonLevel leading up to him, they will have an extremely difficult time dealing enough damage to kill him before running out of EN (energy) or [[{{Mana}} Spirit Points]]. Even when players can keep up with his health regeneration, Don Zauser will likely be picking off allied units one-by-one. Fortunately, he's purely optional and can be evaded by taking another choice from the route split, unless they want to unlock a certain secret in the route featuring Don Zauser.
** If you try to avoid Don Zauser, though, the game pits you against [[Anime/{{Daimos}} Olban]] and he's no walk in the park either. He's a bit similar with Don Zauser that he came after a big-ass MarathonLevel of enemies that are mostly having 5 digits of hit points. After you get him to appear, you learn that he has a tremendous stats, perhaps a bit lesser than Don Zauser and he doesn't even have HP Regen. Doesn't sound like a big problem, right? Well here's the thing: After everything you spent on beating Olban... ''you find out that you just beat up his BodyDouble.'' The REAL Olban shows up afterwards, with ''the exact same robot,'' same tremendous stats and some Shadow Mirror goons for good measure so you have to do the 'beat the hell out of Olban' procedure ''all over again with spent resources''. If you spent the majority of your resources picking off the BodyDouble, you're in for a serious trouble. Oh, and if you think you can just play the long, safe, drawn-out game against Olban? Guess what: Richter is an NPC in the map, and he does not know when to stop attacking anyone in sight, and will attack any enemies, Olban included when opportunity presents itself. Richter might also have boatloads of HP and stats, but it won't be enough to beat Olban, and if he dies, it's GameOver for you!
** Due to how NewGamePlus carries over an OldSaveBonus, the ''A Portable'' remake unwittingly turns [[Anime/MartianSuccessorNadesico Tsukimo Shiratori]] into this on subsequent play-throughs: the remake allows Tsukimo to be recruited as a SecretCharacter, with his "Ace Bonus"[[note]]A character-exclusive pilot skill upon achieving 50 kills[[/note]] doubling the effectiveness of the pilot skill "[[CriticalStatusBuff Prevail]]"[[note]]Increase the pilot's accuracy, evasion stats alongside CriticalHit rate and their unit's armor rating as its respective {{Hit Point}}s decreases[[/note]], which Tsukimo has by default. The problem is if his Ace Bonus is unlocked on a prior play-through, he will have it when he's still a boss unit. That means players have turned Tsukimo into ''another Don Zauser''; while his Daitetsujin doesn't RegeneratingHealth, that matters little when his unit's armor rating spikes to a rough value of '''five thousand''', which makes every attack dealt towards him a measly ten units, regardless of strength, ''including {{Combination Attack}}s''. Naturally, like the Don Zauser example, this can easily be bypassed by taking another route altogether.

* ''VideoGame/SuperRobotWarsAlpha''
** [[Characters/MasouKishin Shu Shirakawa and his Neo Granzon]] in ''Alpha Gaiden'' was the hardest boss in ''Super Robot Wars'' history until he was dethroned. The Neo Granzon goes OneWingedAngel (hence "Neo"), can regenerate HP to full again and again for both player and enemy turns, gets an ExtraTurn for every round AND will use it for two MAP Attacks, which do a ton of damage and may as well destroy all allied units on the field. Perhaps most destructive is the Neo Granzon's "[[SphereOfDestruction Shukutaihou]]" weapon, an attack in all of its appearances almost ALWAYS guarantees a OneHitKill, and only those with exceptionally high armor ratings (re: {{Super Robot}}s) can have a chance to survive. To give a better picture of this, [[VideoGame/SuperRobotWars3 in an earlier game with the Neo Granzon]], the Shukutaihou's base damage is 19400, a number ''even higher'' than the FinalBoss' HP.
** [[Anime/TurnAGundam Gym Ghingham and the Turn X]] in ''Alpha Gaiden'' is also a real bastard on "Hard" difficulty, especially if players want to consider acquiring the "Skill Point". They'll need to haul ass and destroy him, while ignoring the EliteMooks, and pray they can destroy his Zalbak guards, all at the same time. Just to screw with players, Gym regenerates HP and EN at least once and the scenario has a ten turn limit, of which three will be spent just getting to him. How quickly Gym can be taken out largely depends on how much Spirit Points allied characters have left after getting through all that.
** [[Manga/GetterRobo Emperor Gore]] in ''Alpha Gaiden'' regenerates up to '''SIX''' times with mile high HP. The asshole just refuses to die!
** ''Alpha 3'' has [[Anime/{{Dancougar}} Emperor Muge Zorbados]]. By himself, he's not that bad; unfortunately, he's fought in the RealRobot route, thus greatly crippling players' ability to deal out tons of damage and use supers to tank hits. Secondly, a huge assortment of {{Mook}}s follow Muge, with at least a third of them being sub-bosses. To make matters worse, one of the sub-bosses [[{{Brainwashing}} mind controls part of the team from the start]], forcing players to make killing this pilot a priority. Finally, after having pissed away most of the party's Spirit Points dealing with the sub-bosses and {{Mook}}s, Muge enters with 170,000 HP and can do a nice amount of damage, most likely killing off most of the weakened and/or weaker troops, with the stronger ones scraping the bottom of the barrel for ammo by this point, assuming the enemy horde haven't destroyed any allied units who can resupply allies with ammunition and EN.

* ''VideoGame/SuperRobotWarsDestiny''
** [[Anime/MobileSuitVictoryGundam Farah Griffon]]. ''Destiny'' is more known for its collective hordes of evil out for the player's blood that invert the SortingAlgorithmOfEvil, where most bosses are small fry compared to the OriginalGeneration {{Mook}}s; Farah is the exception. She's in the small [[Anime/MobileSuitVictoryGundam Gengaozo]], making her hard to hit, laddled with ''four'' equippable parts to boost accuracy and evasion rates, while the machine has much thicker armor than the average real robot should ever, '''EVER''' have. Worse, she's fought after [[ThatOneLevel one of the most grueling levels in the game]]. It doesn't help that aside from the OriginalGeneration {{Mook}}s, the ''Anime/MobileSuitVictoryGundam'' ones are the DemonicSpiders of ''Destiny''. Farah is the pinnacle of that mind-numbing terror, laughing off the best attacks as the party's Spirit Points dwindle to nothing, players' oft-praised, perfect aces humiliated time and time again by this woman when they can't shoot her down. All this is ''before'' her "[[CriticalStatusBuff Prevail]]"[[note]]The lower the HP, the greater the increase to accuracy/evasion/critical/armor stats[[/note]] pilot skill kicks in.
** The absolute worst boss in ''Destiny'' would have to be [[Anime/{{Macross 7}} Gepelnitch]]. 200,000 HP with one-shot of full HP regeneration once he hits 50%, and a unique pilot skill that halves all damage done to it except song-based weaponry, [[ScrappyMechanic which runs out quickly and cannot be resupplied aside from a meagre pittance of per-turn regeneration]]. This doesn't come anywhere close to Gepelnitch's own natural "HP Regeneration" unit ability; alternatively, players ''can'' [[ManaDrain drain him of Will]] to disable his damage-halving skill, but after two or three attacks, Gepelnitch will have regained enough to turn it back on, rendering the player's attempt meaningless.

* ''VideoGame/SuperRobotWarsOriginalGeneration''
** [[spoiler:[[Characters/SuperRobotWarsOriginalGeneration Dark Brain]]]] in ''Original Generation Gaiden'', who so happens to be the BigBad of the game, but ''not'' the FinalBoss. Use of the ''SP Regen'' purchasable pilot skill[[note]]Regenerate 10 Spirit Points per turn[[/note]], is not just simply ''recommended'', but almost ''necessary'', because of how much he has going for him. [[spoiler:Dark Brain]] has 380,000 HP and the ''HP Regen (Large)'' trait[[note]] Recover 30% of your unit's maximum HP per turn[[/note]], and he can OneHitKill even most fully upgraded units with his attacks. Adding onto this is that there are only six other enemies on the stage, which complicates Will building. These enemies, the Swordian Guards, are effectively EliteMooks, but have stats on par with stage sub-bosses - each one has 200,000 HP, but mercifully lacks HP Regen, so you can afford to take your time at least with them. The Skill Point in this stage is to actually shoot down all of them, which would be a slog even without the boss whipping your units constantly. Because of the huge regeneration, you ''have'' to kill the boss fast. If it only takes you two turns, then that's still 494,000 HP. [[spoiler: Then comes Dark Brain's second phase. Now with 580,000 HP and his strongest attack. His armor is slightly lower, but that's offset by the more than 50% increase to HP. Without the most delicate resource management, you won't be able to out-damage his regeneration. Even only taking two turns on each of Dark Brain's phases is still around 1.25 million HP to go through, which needs application of your best attacks and Spirit Commands throughout.]] There isn't much competition with the scramble to overpower this boss's defenses and weather its attack.
*** To put [[spoiler:Dark Brain]] into perspective, two stages earlier is the fight with [[Characters/SuperRobotWarsCompact3 Shura King Alkaid Nassh,]] who is on ''all counts'' markedly weaker than the above, but is ''still'' enough for this page. Alkaid comes at the end of a MarathonLevel with a bevy of other Shura grunts and most of the remaining Generals, rather than the short, Will-devoid stage listed above. Alkaid's Extim only has 350,000 HP [[spoiler: and its OneWingedAngel form Raha Extim only 450,000, for a sum of 800,000 compared to Dark Brain's 960,000]], its attacks deal less damage, and [[spoiler: When you reach the second phase your units recover all of their SP.]] Even still, it's a desperate situation, forcing you to bring your best - Alkaid still has that 30% per turn heal, after all. [[spoiler: A comparison between Alkaid and Dark Brain can be found in their OverlyLongFightingAnimation attacks - Alkaid can [[MegatonPunch punch you through a mountain.]] Dark Brain can [[EarthShatteringKaboom slam you through planets.]]]]
** Back in the first game, [[spoiler:[[Characters/SuperRobotWarsAlpha Ingram Plisken]] and the R-Gun Rivale]], a machine with more than 100,000 HP (estimated at 150,000, but until reduced to below 99,999, the HP bar is shown as ?????), an exceptionally devastating "[[ChestBlaster Axion Buster]]", a slightly less powerful "[[AttackDrones Gun Slave]]" (with a high ammo count), and a tough melee attack that consumes neither ammo nor EN. The machine also has a large EN pool to allow Axion Buster-abuse, the dreaded "Warp Field" unit ability[[note]]All damage taken is halved[[/note]] and HP/EN Regeneration per turn. Couple this with its pilot's uncanny stats, it makes most real robots without equippable parts that increase mobility useless, while super robot attacks bounce merrily off the "Warp Field". To make matters worse, unlike boss battles afterward, the fight against this boss doesn't give players many places on the battlefield where they can regain HP or EN, if any at all.
*** Additionally, what makes this boss difficult is due to the scenario's "Battle Mastery" requiring players to defeat the boss in as few as ''seven'' turns for the fight. The CombiningMecha SRX gained after reducing its health to a certain threshold not only lacks power (even when spamming Spirit Commands), but is only available for three turns and will fizzle like a torch when tagged with the boss' Gun Slave and Axion Buster. Oh, and the SRX's best attack is ''melee-based'', meaning the boss won't use up any of that Gun Slave ammo.
*** Keep in mind this boss will be fought AGAIN down the road: in fact, the first time it appears, players don't even see it coming, [[spoiler:because the Rivale was hidden in the regular R-Gun all along]].
** Also in the first game is the earlier fight against [[Characters/SuperRobotWarsClassic Bian Zoldark]]. Compared to late-game bosses, Bian's Valsion is profoundly inferior. However, it still has "Warp Field", a massive store of EN to fuel its barrier, attacks that are downright overpowered at that point in the game, and the fact players have to hack through hordes of {{Mook}}s to get to it. They also have to fight the ''even stronger Shu and Granzon'' (but only to acquire the Battle Mastery, which necessitates players to defeat Shu ''before'' going after Bian, all while the latter delivers potshots with the Valsion). At this point in the game, there's only ONE EN-reducing weapon available, which must be reloaded every two rounds - heaven help players if they didn't equip an allied unit with the equippable weapon "Resupply Module"[[note]]Refill an allied unit's ammo and EN to maximum[[/note]]. To clinch this, it's unlikely many allied characters have the "SP Regeneration" pilot skill when fighting Bian, meaning it's a must when rationing off Spirit Commands, all but necessary so as to evade the Valsion's attacks.
** [[Characters/SuperRobotWarsOriginalGeneration Wilhelm von Juergen and the Valsion Custom Type-CF]] in ''Original Generation Gaiden'' (not the bonus "2.5" section of ''[[VideoGameRemake Original Generations]]''). He appears after fighting hordes of Bartolls, each with insane evasion rates (to wit: Using the ODE System, [[HiveMind their wills are unified]], so if one Bartoll unit gets a raise in morale, other Bartolls will gain the same amount, and if you hit one, the rest get more powerful or evasive, requiring you to use the Sure-Hit Spirit Command to consistently hit them and ignore that (and that costs SP)), then pits the party against a BrainwashedAndCrazy [[Characters/SuperRobotWarsAdvance Lamia Loveless]], with the victory condition demanding [[Characters/SuperRobotWarsCompact2 Kyosuke Nanbu]] be the one to deal the final blow (almost impossible without sacrificing some Spirit Points). Finally, in comes Juergen at a whopping 300,000 HP against the drained party, with above average evasion, and since it's unlikely allied units and pilots have been upgraded (either because players are saving for a bigger investment or the fact the game jumps frequently from one point-of-view to the next, making upgrades and [[TechPoints Pilot Points]] sparse), they might not get someone with "SP Regeneration". Just to rub it in, Lamia is unavailable as reinforcements after rescuing her and before even starting the battle with Juergen, any remaining Bartolls might still be around to further harass the party. The silver lining was that if this was the bonus scenario in ''[=OGs=]'', it would have been worse: He brought in a new horde of Bartolls when he arrived (he didn't do it in'' Gaiden'') so you have to fight a new wave along with any Bartolls you didn't destroy yet, and some top units like Sanger and Ratsel became flat out unavailable for that map (for no apparent reason, unlike Lamia). So... yay?
** [[VideoGame/SuperRobotWarsDestiny Perfectio]] in the ''Second Original Generation'', as a result of MarathonLevel. If players want the "SR Point", they have to deal with all current {{Mooks}} on the map before defeating [[Characters/SuperRobotWarsDestiny Ignis]]. Simple enough, but then they have to face off against [[Characters/SuperRobotWarsDestiny Umbra]] with {{Mook}} reinforcements. Again, still simple, and once Umbra's gone, Perfectio finally appears. At the start of every turn, he ''automatically reduces the entire party's Will'', his Fatum has an exceptionally large EN pool, making it futile to burn it away to prevent him from using the Fatum's strongest attacks, can [[ExtraTurn move twice]] and worst of all, ''regenerates HP to full'' '''TWICE''' due to in-game events, even taking cues from Shu in ''Alpha Gaiden'': in-between regenerating, Perfectio will ALSO cast Spirit Commands on himself. Compared to the [[Characters/SuperRobotWarsMX AI-1]], [[Characters/SuperRobotWarsAlpha Son Ganlong]], the FinalBoss and TrueFinalBoss, Perfectio is ThatOneBoss for this game. Oh, and did we mention that unlike its predecessors, the ''Second Original Generation'' prevents any purchase of the "SP Regeneration" and "[[MinMaxersDelight Attacker]]" pilots skills[[note]]At 130 Will, increase damage dealt by 20%[[/note]]?
** AI-1 is a [[BreatherBoss step down]] from Perfectio, but it has HP Regeneration, the "Counter" pilot skill[[note]]Gain a chance to attack first before the opposing unit can during its attacking phase[[/note]] and weapons that reduce units' mobility. However, what's unique about the AI-1 is players ''cannot drain its EN dry'' because of its exclusive unit ability turning 1% of all damage received into EN, making its "TE Sphere" damage-reducing barrier operate almost 100% of the time. Combined with the fact that barrier-breaking weapons are less common in the ''Second Original Generation'', the AI-1 can be a hassle, but nowhere as frustrating as Perfectio.
** Son Ganlong is really a DamageSpongeBoss; however, if the player is attempting the SR Point, be prepared for a marathon. Granted, [[spoiler:[[Characters/SuperRobotWarsAlpha Kukuru]] pulls a HeelFaceTurn in this scenario and joins the party until the end of the game]], but you must contend with the [[Characters/SuperRobotWarsOriginalGeneration KyuKiOh]] and [=TouTetsuOh=] again, alongside [[Characters/SuperRobotWarsOriginalGeneration Kanan and Sandaiyuu Taihou with the JakuBuOh/BuJakuOh]]. Oh, and the requirements for the SR Point? "Destroy ''all enemies before'' destroying Ganlong's [=OhRyuOh=]". To twist the knife further, the [=KyuKiOh=] and [=TouTetsuOh=] have a pre-movement MAP aura that ''drains Will Points'' with one of the [=TouTetsOh's=] attacks that ''drains Spirit Points'' and attacking Taihou in the [=BuJakuOh=] long enough forces him to regenerate his unit to full HP, giving Kanan the controls to the [=JakuBuOh=] (though the [=JakuBuOh=] is defensively weaker, making it easier to take down). By the time all four of them are defeated, the player has likely exhausted a majority of the party, and must deal with a size LL, barrier-enabling, MAP attacking [=OhRyuOh=].
** If players are aiming for the SR Point in the Hard route for the scenario against the FinalBoss [[spoiler:[[Characters/SuperRobotWarsAlpha2 Nashim Gan Eden]]]] in the ''Second Original Generation'', they have five turns to destroy the three mini-bosses, each with HP exceeding 150,000, on top of an "Ace Bonus"[[note]]An exclusive unit ability given when 50 kills are achieved[[/note]] that grants ''S-ranking adaptability on all terrains''. This forces players to throw tons of Spirit Commands when dealing with them; however, leave just one with little HP remaining at the end of the player's fifth turn, and the FinalBoss appears on the enemy turn, who automatically ''heals all enemy units on the battlefield by 50% of their HP'', rendering players' efforts moot. Even if they don't aim for the SR Point, the recovery still produces problems. As for the boss itself, it has a barrier with similar properties to Warp Field, including an exclusive barrier bonus that further reduces damage, ''determined by the number of enemy units left on the field''. Its strongest attack also drains EN.
** The TrueFinalBoss of the ''Second Original Generation'', [[spoiler:[[Characters/SuperRobotWarsAlpha Euzeth Gozzo]]]], in addition to summoning previous mini-bosses fought in the game, has a unit with a similar EN-absorbing ability as the AI-1 (though it spends EN much less than the AI-1; instead, most of its weapons are ammo-based), and the boss has a very nasty ability that allows him to '''move three times per turn''' after his Will exceeds 160. Furthermore, he's one of the few bosses in the game with the "Revenge" pilot skill[[note]]Increase counterattack damage by 10%[[/note]] and his unit's MAP Attack, if successfully hit, prevents allied characters from using Spirit Commands for a turn, rendering defensive Spirit Commands cast against MAP Attacks pointless. Also, when his unit's HP is brought down to its last 10%, ''its hit rate against your units becomes 100%''. Combined with a very high accuracy rating, S-ranking for all terrain adaptability, maximum level "Prevail" and level 9 "Telekinesis"[[note]]increases accuracy and evasion for every level up to 9[[/note]] pilot skills, he is close, but not enough to edge [[spoiler:Dark Brain]] off of his throne.
** The FinalBoss [[spoiler:[[Characters/SuperRobotWarsOriginalGeneration Qepaloc Narmo]]]] for the ''Dark Prison'' DownloadableContent. Granted, it's just a battleship, until players realize its size is "LL", while the rest of the party contain units from size "M" to "L". Secondly, the boss has tons of {{Mook}}s, forcing players to inch their way through to get to him. Next, he can attack twice, with an Ace Bonus allowing him to cast the "Zeal" Spirit Command[[note]]Grants the unit an ExtraTurn[[/note]] at the start of the enemy phase when his HP falls below 30%. Its MAP Attack is ammo-based, boasting ''30 rounds'', to which he WILL use ''every single turn''. Finally, the party consists of only ten units available: four to begin with, three are {{Guest Star Party Member}}s and their units cannot be upgraded, and the rest aren't available at the start of the scenario. Not only do players not get enough room to breathe, but if any ally is destroyed during the scenario, ''it's an automatic game over''. All this is ''before'' any mention of [[HarderThanHard EX-Hard Mode]] where suddenly, it can actually ''hurt [[GameBreaker the]] [[SuperToughness Neo]] [[EleventhHourSuperpower Granzon]]''. Needless to say, prepare for a slug fest.
** ''The Moon Dwellers'' Chapter 42. You prepare to face [[spoiler: ''VideoGame/SuperRobotWarsGC''[='=]s final boss: Helluga Izberga]]. He's sitting on a Cross Gate, at the opposite side of the map, that gives him infinite EN (so forget about EN-draining moves, especially since his infinite EN takes the form of his attacks being free to use). He has a lot of HP and is accompanied by units whose HP range between 12,000-42,000. You start taking down his minions and once you get to him, reinforcements arrive in Zuvorg grunts and a boss unit. The boss unit has a FULL MAP ATTACK that [[PercentDamageAttack halves four random units' HP]] and can't be blocked. Then after a few turns, Helluga also gets a full MAP Attack, which doesn't hurt as much, dealing roughly 10% of the target's current HP in damage but hits ''everybody'' on the map. [[ThatOneAttack Those two attacks]] combined will crush an unprepared player especially if you try to take the SR point (Kill everyone within 15 turns before Helluga, which can take quite a few turns since the other enemies are spread out and don't start moving until someone gets close to them). The only way for this boss to not be ThatOneBoss is to rush the boss and to ignore the grunts. By the time the Zuvorg units come, he'll already be weakened and you'll only suffer the GameBreaker Map Attacks once or twice.
** In the same game, a few missions later, [[VideoGame/SuperRobotWarsJudgment Gu-Landon Gorz]] ups his ante from his rather AntiClimaxBoss performance in his original game. First, before reaching him, you'll have to contend with Kalo-Ran and have to beat him in 6 turns in order to get a Skill Point, which will likely exhaust your SP. When he appears, he sics a few Vorlents on you, and like [[spoiler:Helluga]], he gets a double turn; with his long range attack, he can snipe you with ease while the Vorlents need to be taken care of. And just as you march toward him, he then does one thing most bosses didn't do: He ''moves'', screwing your possible prepared formation. And as you damage him, he activates multiple Spirit Commands, and eventually unlocks his ultimate attack that could kill a low armor RealRobot in one hit if not defended. Eventually, one of these Spirit Commands include ''Iron Wall'', meaning that unless you want to waste your Valor-enhanced attacks ''reduced'' to measly 3000+ damage attacks, you better end your whole turn, meaning that anyone that has activated an extra turn (through Impetus) just wasted their SP, and then he gets some free shots on your team, ''including a damaging MAP Attack'', that again can kill squishy allies in one hit if they didn't dodge. The Iron Wall activation happens ''twice''. Take all those, and unlike the original game, he has no ClippedWingAngel form, meaning that he gets to keep all those damage-reducing Orgone Clouds throughout the whole battle. Needless to say, get ready for a slugfest and be prepared to lose a few units... and [[HeroMustSurvive one of those units better not be Touya and his Granteed Dracodeus]], hope you've been upgrading him.

* ''VideoGame/SuperRobotWarsUX''
** Don't let the [[HeroicSecondWind full recovery event]] fool you, but [[spoiler:Kali Yuga]] is probably one of the hardest bosses for [=SRW=] handhelds. First off, all of its attacks inflict StatusEffects (one of which halves a pilot's stats), meaning without someone like [[VideoGame/VirtualOn Fei-Yen HD]] using her Tactician Bonus "Spiritual Fortitude"[[note]]negates Spirit Point, stat and Will decreases, and still perform any action[[/note]], players are likely screwed. Secondly, due to most allied units having a size rating of "SS" to M (with just a few being size L), the boss towers above everything with the extremely rare size of '''3L''', meaning the largest defensive and offensive bonuses in the game. Combined with a list of pilot skills such as a max level "Prevail", "Guard"[[note]]At 130 Will, decrease all damage received by 20%[[/note]] and "Counter", alongside high armor and stats for everything, even if players fully commit to using Spirit Commands against it, without a high enough evasion rate, it can attack first via "Counter" and reduce allied attackers' stats by half, rendering their attacks pointless. The catch for the fight is players must fight another boss beforehand (which is no cakewalk, either) ''and'' they have to deal at least 30% damage to the FinalBoss in order to trigger the HeroicSecondWind event. Given the gameplay system of ''UX'' (no equippable parts and fewer Spirit Points for sub-pilots) is pretty different from handheld titles before it, this makes [[spoiler:[[VideoGame/SuperRobotWarsZ Gaiou]]]] look that much easier.

* ''VideoGame/SuperRobotWarsW''
** Although players often consider handheld titles (especially those on the Platform/GameBoyAdvance and Platform/NintendoDS) a lot easier than console installments, there are a few spikes that can hurt. For example, [[Literature/FullMetalPanic Gauron]]: in this game, he will be fought three times, the former two requiring some real tough nuts to crack. To elaborate, his mecha (be it the Codarl or Venom) has some really nasty long-ranged attacks (along with his "Combo" pilot skill[[note]]Consecutively attack adjacent enemy units[[/note]]), the "Lambda Driver" unit ability can reduce damage and is an equivalent of "Afterimage", Gauron can reach up to 170 Will, and worst of all, '''HE WILL USE SPIRIT COMMANDS ON EVERY TURN''' (namely "Focus"[[note]]Increase accuracy and evasion rate by 30% for one turn[[/note]] and "Zeal") and has "Prevail", too. Quite a chunk of players consider this sadistic bastard even stronger than the FinalBoss for ''W'', given the situation. Below are the breakdowns of the two hard encounters:
*** In Scenario 9 of the Earth Route, the units available are those from the [[Anime/{{GaoGaiGar}} Gutsy Galaxy Geoid]], [[Literature/FullMetalPanic Mithril]], [[Anime/MobileSuitGundamWingEndlessWaltz the colony Gundams]] and the OriginalGeneration. That's not too bad, considering the units contain the largest number of {{Game Breaker}}s in ''W'', except it's still early in the playthrough, and their Spirit Points are limited (including the number of upgrades players have probably not applied yet), meaning they're unlikely to frequently use the "Strike" Spirit Command[[note]][[AlwaysAccurateAttack Gain 100% accuracy for one turn]][[/note]]. The key to defeating Gauron, [[Anime/{{GaoGaiGar}} Mic Sounders]] (who has a weapon that reduces enemy mobility by 50% for one turn), probably spent most of his Spirit Points to survive the onslaught earlier before TheCavalry arrives. Since the scenario takes place on a base, if Gauron moves onto the base structures (via normal movement or in-game events), he'll gain HP/EN regeneration, including defensive and evasion buffs, from the buildings. If players are playing normally, they won't have any means to reduce his Will. Even after that, players must contend with [[Anime/MobileSuitGundamWingEndlessWaltz Chang Wufei in the Altron Gundam]] and [[Anime/MobileSuitGundamWingEndlessWaltz Trowa Barton]] along with enemy reinforcements, while [[Literature/FullMetalPanic Sousuke Sagara, Kurz Weber]] or [[Anime/MobileSuitGundamWingEndlessWaltz Heero Yuy]] must survive the scenario. There's a reason why experienced players tell newcomers to ''W'' to choose the Space Route instead of the Earth Route for the first route split of a playthrough.
*** The second time Gauron appears is in Scenario 35. Team-wise, players are in better shape than before (thanks to the rest of the Gutsy Galaxy Geoid and the ''Anime/TekkamanBlade'' [[GameBreaker bunch]]), and plenty characters have learned the "Strike" Spirit Command. Of course, before fighting Gauron, a group of EliteMooks must be dealt with first, but if overeager players think about taking Gauron out ASAP, think again: damage him once and he'll regenerate HP to max AND instantly cast "Strike" and "Valor" immediately. If allied units are sticking together (especially Sousuke or [[Literature/FullMetalPanic Melissa Mao]], who cannot die in this scenario), they're going to get hurt badly because of Gauron's "Combo" pilot skill.
*** Fortunately, the third encounter in the next scenario is far easier, as Gauron stops casting Spirit Commands.
*** Some players argue Gauron is just as difficult in ''VideoGame/SuperRobotWarsJudgment'' compared to his counterpart here: while he cannot spam Spirit Commands in that game, his stats are roughly above 200 and the "Lambda Driver" ability for his mecha are just as effective there. The only units most likely to hit him without using Spirit Commands are [[Anime/BrainPowerd Yuu and Hime]] using the cost-effective "[[CombinationAttack Chakra Extension]]". Additionally, the Venom does not regenerate HP, nor are there any HP/EN regeneration panels on the battlefield when he appears in scenarios. Compared to ''W'', he is slightly easier in ''Judgment''.

* ''VideoGame/SuperRobotWarsZ''
** The FinalBoss [[spoiler:[[Characters/SuperRobotWarsZ The Edel Bernal]]]], if [[Characters/SuperRobotWarsZ Rand Travis]] is chosen as the protagonist. The difficulty curve of a ''Z'' playthrough varies between average to decently hard to easy through use of {{Game Breaker}}s, but the FinalBoss is much, ''much'' harder than anything before him, including the [[Anime/OvermanKingGainer Overdevil]]. He has the highest HP in the game (250,000 to 400,000 depending on the difficulty; ''Z'' [[{{Cap}} doesn't allow more than 30,000 points of damage dealt]], even when using the strongest attack in the game stacked with buffs), has HP Regeneration, the usual assortment of overpowered ALL and MAP Attacks, can move twice and earns an additional +2 Will every time when hit, enabling the use of both MAP Attacks (one at 110 Will, the other at 130). On Hard difficulty, he gains five rounds for each MAP Attack, the stronger one now requiring only 120 Will. To top it off, players must fight TWO OTHER COPIES OF HIMSELF, each with the same skills, statistics and weaponry. But it doesn't end there: to achieve the victory conditions, the FinalBoss and his copies must be destroyed '''ON THE SAME TURN''' or they'll regenerate HP to full. Like Perfectio in the ''Second Original Generation'', the final scenario is a MarathonLevel, a very long 3-part map which begins with a tough boss fight, followed by a barrage of {{Mook}}s with no intermission in-between. Woe betide the poor player who used their consumable, equippable parts or wants to rearrange their squad formations. Since SaveScumming is likely in effect, the scenario can become {{Unwinnable}} very easily with one small mistake. Imagine doing this on "[[HarderThanHard EX-Hard Mode]]", where all upgrades to pilots and units are barred...
*** The FinalBoss becomes laughably easy if [[Characters/SuperRobotWarsZ Setsuko Ohara]] is the protagonist, since there are no copies, only a statistically stronger version of him. Because he only has A-rank for terrain adaptability, allied units with S-ranks will be a lot safer.
** With ''Literature/FullMetalPanic'' appearing in ''Jigoku-hen'', players knew Gauron would retain his status, and that he does: appearing as earlier as Scenario 8, he comes fully-decked with "Prevail", "Guard", "Counter", and "Ignore Size Modifier". With his Codarl's "Lambda Driver", the only unit to really take a few hits at this point in the game is the [[Anime/ShinMazinger Mazinger Z]], while the most effective way to damage him is through "[[AttackPatternAlpha Maximum Break]]", which is tricky to use if one still hasn't grasped the "Tag Tension System". Some players will likely start upgrading Sousuke's M9 so that he can stand on his own against Gauron and for future reappearances, but unfortunately, his M9 doesn't share upgrades with ARX-7 Arbalest.
** OriginalGeneration bosses throughout the ''Z'' series aren't generally hard, barring some of them depending on the playthrough (such as a [[spoiler:Level 99 Gaioh]] from the ''Second Z''), but [[Characters/SuperRobotWarsZ Gadlight Meonsam and the Geminia]] in ''Jigoku-hen'' is an exception. His pilot skills are nothing short of impressive: "Genius"[[note]]+20 to accuracy and evasion stats and critical hit rate[[/note]], max level "Telekinesis" and "Counter", and a level 8 "Prevail". His Ace Bonus automatically casts the Spirit Command "Strike" at 130 Will, and worst of all, can take '''THREE ACTIONS PER TURN''' thanks to the "Triple Action" pilot skill, which he's sure to use to blast the party well away with his extremely wide-ranged and powerful MAP Attack. Oh, and if players believe scattered {{Mook}}s among the map can protect the party from his MAP Attack? No: [[UnfriendlyFire he will just use it like it's nothing]].
*** If you think all of ''that'''s bad, try fighting him in ''Rengoku-hen'' with only ''six characters''. Thankfully, Gadlight doesn't start out strong as he only got 46000 hit points and has Double Action. However, he'll still use that MAP attack and there's nothing you can do to stop it from happening. Oh, and you need to beat him in ''five turns'' for the SR Point. Have fun with that.
** [[Anime/TengenToppaGurrenLagann The Anti-Spiral King and their Granzeboma]] is similarly difficult, with pilot skills largely the same as [[spoiler:Gadlight]], a wide MAP Attack with [[UnfriendlyFire indiscriminate fire]] included (though it only moves twice per turn and its "Prevail" level is at 7). Unfortunately, the Anti-Spiral King takes a page from Perfectio, with their Ace Bonus reducing allied characters' Will by 5 each turn. Due to in-game events, the size of all units is locked at "infinite", making not only the "Ignore Size Modifier" pilot skill[[note]]No accuracy or damage penalties incurred when attacking a unit of a larger size[[/note]] meaningless, but the fight completely depends on statistics, unit upgrades and Spirit Commands. Meanwhile, the Anti-Spiral King have incredibly high base stats, will immediately attack the party on the first turn, and to acquire the SR Point, their HP must be reduced to 99,999 ''within 4 turns''. There's a good reason this is the FinalBoss of ''Jigoku-hen''.
** If you loathe Gadlight above, try not to throw the controller when playing ''Tengoku-hen'', because '''every single Original boss''' in there can move AT LEAST three times per turn. Especially all the Sphere Reactors from Sidereal: not only do they all have impressive stats, skills and terrifying Ace Bonuses, but their units' [[AreaOfEffect Sphere Act]] have an absurd range of ''10 GRIDS'' with various effects: Shiku's Shiseiten stops all kind of SP Regeneration, Straus [[spoiler:(Elunaluna)]]'s Pleiades Taura [[ManaDrain absorb 40 EN from every enemy unit per turn]], Barbiel's An Ares [[DamageIncreasingDebuff reduces all enemies' armour value]], and Emperor Australis [[spoiler:(Dimensional General Wildark)]] reduces all damage dealt by enemies in the area. They are the reasons why Stage 15 and Stage 48 [[ThatOneLevel are so frigging difficult]]. Fortunately, their Sphere Acts can only activate upon reaching 140 will, so it's important to keep an eye on that. Your only saving grace is when Australis [[spoiler: turns into Wildark]] for the HeroicSecondWind to kick in, but good luck getting there.
** As the TrueFinalBoss for the ''Z'' series, [[spoiler:Saint Advent and Supreme God Z]] isn't something to be mocked at, even if you think you can plough through it after Z-Blue [[spoiler:achieves Shinka Fusion]]. First off, as a rare case in the franchise, the last stage ''has a time limit'' of 9 turns where it doesn't even show up before Turn 4. And then, just like the incarnation before and as the first in the franchise, [[spoiler:Saint Advent]] can move '''FOUR TIMES PER TURN''' after reaching 130 Will; and on Hard Difficulty, [[spoiler:he]] will fire up to 150 Will after showing up. It can also deal significant damage to random units (the number of units being hit will also increase) at the start of each turn. Combined with [[spoiler:his]] crazy stats and enemy-only skill "Pressure"[[note]]Reduces damage taken while dealing more damage taken in return if the bearer's Skill value is higher than the opponent; the effective area is the skill level times 4[[/note]], extremely high armour value at '''4500''', HP/EN regeneration and very damaging attacks, [[spoiler:he]] is a very hard boss to tackle with. [[ButWaitTheresMore Except there're more to come:]] After taking down its' HP to half, the generic HeroicSecondWind kicks in......but unlike that from recent games, ''your units don't receive any sort of recovery'' after that. That means players have to manage their units' status well when fighting a boss with an absurd 750K HP, who takes even less damage after the event [[spoiler:as Saint Advent now has the Prevail skill]]. What's more, [[BossInMookClothing 12 Zel Millennium]] spawns around (fully decked with high HP and MAP weapons) ''will activate their [[spoiler:Fake Sphere Act]]'' if left unattended. Now that's one hell of a TrueFinalBoss.

* ''VideoGame/SuperRobotWarsBX''
** Say what you will about the series itself, if you underestimate [[Anime/MobileSuitGundamAGE Vegangear Sid]] in Stage 41, your team will be '''DESTROYED''', no "if"s, "and"s or "but"s. First off, the unit and Zera Gins himself have almost all of the best skills available for a unit and pilot: For the unit, it has Level 3 HP and EN Regeneration, Afterimage, All S on Terrain Adaptability, Machine Block (NoSell any spec-lowering effects) AND a MAP Weapon with a huge coverage range while being '''FriendlyFireproof'''; as for Zera, he is fully-decked with the highest level of X-Rounder, Prevail ''and'' Pressure, as well as Exceed Will Limit, Counter, Guard, and more. All of these combined make the machine itself so much of a LightningBruiser that even fully-upgraded units can't achieve a 100% hit rate against it, while it can hit ANY of your units at an unusually high hit rate. Then there's the fact that Stage 41 is an [[MarathonLevel extremely long stage]] (as it resolves both the plotlines of ''[[Anime/MobileSuitGundamAGE Gundam AGE]]'' and ''[[Anime/MartianSuccessorNadesico Nadesico]]'') while you have a smaller sortie headcount than normal, against huge waves of mooks and a series of named bosses including Zeheart Garette and his Gundam Legilis, who is certainly not a cakewalk. [[ButWaitTheresMore Feel tired already?]] Once Zanald Beihart's Xamdrag and [[Anime/MartianSuccessorNadesico Haruki Kusakabe's Kaguraduki]] show up along with the La Gramis Fortress in the background, Vegangear Sid's danger level kicks up to the max as it can enjoy ''BOTH'' of their Command benefits along with the Fortress' Terrain bonus for evasion and defense, and if you're able to save some of the secret characters? You have to protect them from being destroyed as well, even if their positions are so inconvenient. Vegangear Sid will also recover a maximum of 4 times, and [[GuideDangIt if you take out the named characters in the wrong order]], you may wind up fighting this monster with ''over 300,000 health''. A lot of players agree that this is EVEN STRONGER than [[spoiler:both]] FinalBoss[[spoiler:es]] of the game, and it's certainly not a bluff.

* ''VideoGame/SuperRobotWarsT''
** Coming at the tail end of Scenario 34, we have the climax boss of ''Manga/MagicKnightRayearth'', [[spoiler:Emeraude,]] who fulfills this trope in spades. She may have only one attack, but she has roughly double the HP of the previous boss of the stage, Zagato, comes in with the "Supreme", "Pressure Level 4" and "Triple Action" skills. If you do not take her out quickly, you will lose the fight. To put it in perspective, she can nearly one-shot battleships and tanky Super Robot units alike. Also, she will make a beeline towards Hikaru, focusing completely on her and can easily one-shot her, resulting in a Game Over.

* ''VideoGame/SuperRobotWars30''
** Returning from ''T'', we have [[spoiler:Emeraude]] once again. Everything that made her a pain to fight in ''T'' is present and accounted for here, including her obscenely high health pool, incredibly damaging attacks, her tendency to target Hikaru, and coming right off the heels of an already challenging boss fight with Zagato. It actually may be even ''harder'' than the version of the fight in ''T'', since unlike there, where [[spoiler:Emeraude]] fights alone, here the boss is backed up by two squads of [[Anime/MazingerZInfinity Kikaiju]] and [[Anime/SSSSGridman Kaiju]]. At the same time, this can be [[InvertedTrope Inverted]] if you save this map for later, after preparing well-enough.
** [[Anime/ShinkansenHenkeiRoboShinkalion Valdor]] in the Expansion Pack. Before you can even face him, you have to fight through a wave of beefed up Quaestors (Or [[spoiler:Etrangers]] if you're in the postgame), which is bound to waste some of your ammo, energy and potentially health. And when Valdor does spawn, he does so with a fully upgraded and primed Guard skill, meaning that all but the most damaging of your attacks will barely even scratch him. Not only that, but he has incredibly high attack damage, and if able to he will almost always exclusively target Hayato, and the mission fails if he goes down.