History YMMV / KingdomRush

** Umbra, the FinalBoss of ''Frontiers'' is a brutal fight even by final boss standards. It seems like a standard FlunkyBoss at first, but when you "kill" it, it explodes into many small blobs which you must destroy as much of because they'll reform into the boss (but its Maximum Health will be lower if you killed some of them). The battle only gets harder after the first reform as it then uses EyeBeams to ''outright destroy'' your towers, being one of two enemies in the ''entire series'' that can do so, making it harder to kill his smaller Mooks. What makes Umbra ''far'' tougher than the Spider Goddess, the series' other tower-destroying boss, is that Umbra can use it unlimited times while the Spider Goddess only uses hers thrice in the entire fight. In order to beat him, you need to keep killing him and his blobs before he destroys your defenses and his hordes get through.

** Umbra, the FinalBoss of ''Frontiers'' is a brutal fight even by final boss standards. It seems like a standard FlunkyBoss at first, but when you "kill" it, it explodes into many small blobs which you must destroy as much of because they'll reform into the boss (but its Maximum Health will be lower if you killed some of them). The battle only gets harder after the first reform as it then uses EyeBeams to ''outright destroy'' your towers, being one of two enemies in the ''entire series'' that can do so, making it harder to kill his smaller Mooks. In order to beat him, you need to keep killing him and his blobs before he destroys your defenses and his hordes get through. What makes Umbra ''far'' tougher than the Spider Goddess, the series' other tower-destroying boss, is that Umbra can use it unlimited times while the Spider Goddess only uses hers thrice in the entire fight.

* ThatOneAttack: In ''Vengeance'', we have the Anurian Chasers' [[InASingleBound leap attack]]. When they get within a rather generous distance to your troops, they perform a leap that not only [[DungeonBypass clears a good bit of the lane]], but the landing also deals a moderately damaging area ShockwaveStomp. The main reason why it's an attack you don't want to see is that they [[ZergRush appear in huge numbers]], and all of them using this can and ''will'' whittle down Barracks troops while easily sending the group of frogs forwards past a third to half of your towers. Worst of all, this attack has little to no cooldown and they can immediately hop to your next set of troops to bypass more area and plow through them.

** Umbra, the FinalBoss of ''Frontiers''. It seems like a standard FlunkyBoss at first, but when you "kill" it, it explodes into many small blobs which you must destroy as much of because they'll reform into the boss (but its Maximum Health will be lower if you killed some of them). The battle only gets harder as it goes on as it then uses EyeBeams to outright ''destroy'' your towers (This is ''one of two enemies in the entire series'' that can do so), making it harder to kill his smaller Mooks. In order to beat him, you need to keep killing him and his blobs before he destroys your defenses and his hordes get through. Unlike the Spider Goddess from ''Origins'' who can use her "Destroy a Tower" move only thrice in the entire fight, Umbra can use theirs as many times as they want.

** Snow Golems in the Frozen Nightmare expansion initially appear on several spots on the map including areas near your exit. They're dormant until a certain wave passes, after which they get up as a slow but powerful enemy with ''very'' high HP that drops a paltry 25 gold on defeat. To get rid of them prematurely you can pay a huge 200 gold to drop a bomb on their dormant bodies, which gives you a SadisticChoice: Spend a huge amount of gold or fight an annoyingly tough enemy that drops chump change which can be spawned near your exit. Thankfully, the cost needed to bomb them is reduced to 100 gold in Heroic challenges, [[AntiFrustrationFeature and they do not appear in Iron Challenges at all]].

** The low-pitched "OORGH" that most {{Giant Mook}}s make on death.

** Umbra, the FinalBoss of ''Frontiers''. It seems like a standard FlunkyBoss at first, but when you "kill" it, it explodes into many small blobs which you must destroy as much of because they'll reform into the boss (but its Maximum Health will be lower if you killed some of them). The battle only gets harder as it goes on as it then uses EyeBeams to outright ''destroy'' your towers (This is ''one of two enemies in the entire series'' that can do so), making it harder to kill his smaller Mooks. In order to beat him, you need to keep killing him and his blobs before he destroys your defenses and his hordes get through.

*** Perhaps the most severe example of this would be the [[GoddamnedBats Saurian Deathcoils]], whose attack is a powerful, armor-piercing crossbow bolt that has a range of ''nearly half the screen''. As such, they can easily pick off your barracks, skeletons, and heroes before you even have a chance to move them. For this, they're considered to be one of the [[GoddamnedBats most annoying and hated enemies]] in the entire series, though they thankfully only appear in one level.

*** Perhaps the most severe example of this would be the [[GoddamnedBats Saurian Deathcoils]], whose attack is a powerful, armor-piercing crossbow bolt that has a range of ''nearly half the screen''. As such, they can easily pick off your barracks, skeletons, and heroes before you even have a chance to move them. For this, they're considered to be one of the most annoying and hated enemies in the entire series, though they thankfully only appear in one level.

* MemeticMutation: Necromancers[[labelnote:Explanation]]Youtuber Voduke regularly made Kingdom Rush polls comparing towers, where the fanbase constantly voted for Necromancers to the point where it became a meme. It got to the point where Necromancers became an option in polls where it was otherwise irrelevant, which people kept voting for regardless.[[/labelnote]]

* MemeticMutation: Necromancer[[labelnote:Explanation]]Youtuber Voduke regularly made Kingdom Rush polls comparing towers, where the fanbase tended to vote for Necromancers. It got to the point where "Necromancer" became an option in polls where it was otherwise irrelevant, which people kept voting for regardless.[[/labelnote]]

* MemeticMutation: Necromancer[[labelnote:Explanation]]Youtuber Voduke regularly made Kingdom Rush polls comparing towers, where the fanbase tended to vote for Necromancers. It got to the point where "Necromancer" became an option in polls where it was otherwise irrelevant, which people kept voting for regardless.[[/note]]

** Lord Blackburn from the original is up there as one of the toughest bosses in the series. He has a very dangerous ability to temporarily stun your units and up to EIGHT towers within a ''massive'' range, deals heavy area damage making him hard to block even with Paladins, gets a rather short distance to your exit, has [[HeavilyArmoredMook 90% physical resistance]] (due to being a TinTyrant) which makes magic towers a must, and several of his flunkies are highly resistant to magic. Speaking of which, a number of his flunkies are [[GoddamnedBats annoying]] (Black Hags) or [[DemonicSpiders outright dangerous]] (Lycans, Fallen Knights), compounding things further. Mercifully, he's the only boss in the first game who has all his minions die and the waves of enemies stop appearing once he goes down.

** The spell that Tristen and Umber got the dark warlocks to cast is likely the same spell that Lord Blackburn got his White Witches to cast. Both instances had their once-verdant kingdoms turned into haunted wastelands, and their people turned into monsters -- incidentally, both Lord Blackburn and the Ghost Kings have werewolves and skeletons as part of their armies. Furthermore, the spells also turned all three leaders into undying spirits cursed to live on forever.

* AnticlimaxBoss: The Dragon King from ''Vengeance'' can be turned into one with the Blazing Gem. Despite having a huge amount of health, there's a spot at the bottom left that appears tailor-made for placing a maxed-out Blazing Gem with Gem of Amplification to target him. Since the Dragon King doesn't move until 30 seconds pass, the Blazing Gem will lock onto him and ''destroy'' his health in seconds, crippling him before he can move or with prior dps, defeating him before he can move ''once''.

* AnticlimaxBoss: The Dragon King from ''Vengeance'' can be turned into one with a maxed Blazing Gem. Despite having a huge amount of health, there's a spot at the bottom left that appears tailor-made for placing a maxed-out Blazing Gem to target him. Since he doesn't move until 30 seconds pass, the Blazing Gem will lock onto him and ''destroy'' his health in seconds, crippling him before he can move or with prior dps, defeating him before he can move ''once''.

** There's a pretty good reason why Mactans [[TheUnfought never fights you directly]]. She's only as big as a Son of Sarelgaz. While those are durable, armored, and magically resistant, a single one isn't much trouble to defeat for a late-game defense. Thus, Mactans avoids direct combat with your towers as they would end her very quickly.

** Maginia Shores from Vengeance is often seen as a ridiculous jump in difficulty from the main game, even by Elite Stage standards. You are just simply bum-rushed by a horde of heavily armored enemies, but they each have their own tricks so you can't just pound them with magic (Chasers leap onto your troops to bypass your towers and Wardens have their shields replaced by Infusers). The waves involving Wardens and Infusers can get especially hairy, as the game chucks so many of them at once despite having very good armor.

** The [[http://hyperduck.bandcamp.com/track/rising-tide-preparation prepration]] and [[http://hyperduck.bandcamp.com/track/rising-tides-battle battle]] themes for the [[BrutalBonusLevel Rising Tides]] levels in ''Frontiers''.

* SequelDifficultyDrop: Compared to the original, ''Frontiers'' and ''Origins'', this game has enemies that generally aren't as tough ({{Giant Mook}}s have less HP overall although they sport armor) and allows you to use specialized towers from the get-go instead of having to level a tower to its maximum level to get its specialization.
* ThatOneAchievement: In ''Frontiers'', there are a few achievements that stand out among the players as the hardest to get due to it requiring a lot of [[FakeDifficulty luck]] and/or [[{{Padding}} time]]:

** The [[https://www.youtube.com/watch?v=bFPIU2EPVt0 Anurian battle theme]] in ''Vengeance'' is a quick and fast music that gives the feel of a subaquatic, froggy threat, appropriate for a BrutalBonusLevel.

** After 15 brutal waves in [[BrutalBonusLevel the Sunken Citadel]], Leviathan comes out as this. His extremely slow movement, lack of useful tricks (his only ability - stopping to disable certain towers next to the coast for a second - makes him stop while doing so) and weak minions (Greenfins, Deviltides, Redspines, the DemonicSpiders only appear if you take too long) make him pale in comparison to his own EliteMooks.

* DisappointingLastLevel: The cave stages in ''Frontiers''. Much of the puzzle-like elements to beat a level is gone. Your towers and powers have levelled up beyond anything the enemy can throw at you and the levels can be sweeped through sheer firepower because there are no ultra-heavy armored foes and only one caster type, which downplays the TacticalRockPaperScissors aspect of the previous stages a lot. The initial funds are much higher, which allows for a much less strict and more relaxed planning in the early waves.

** There's a pretty good reason why Mactans [[TheUnfought never fights you directly]]. She's only as big as a Son of Sarelgaz. While those are durable, armored and magically resistant, a single one isn't much trouble to defeat for a late-game defence. Thus, Mactans avoids direct combat with your towers as they would end her very quickly.

** Despite being a Bluegale, who are [[AntiMagic immune to magic]], Jun'Pai lacks any magic resistance. His bio states that the Trident he wields would kill anyone not capable of handling the intense magic within, and that he has to endure the energy running through it. As such, he loses all his magic resistance by handling his trident in order to prevent it from killing him.

** [[spoiler: Vez'nan. He periodically casts a spell that renders a large number of your towers temporarily unusable (which is ''very'' annoying), and kills normal soldiers in one hit, but he doesn't have that much health.]]

** Gerald Lightseeker in ''Vengeance''. Not difficult and lacks a strong [=AoE=], but has a good bit of physical armor and like Baj'Nimen above he can also reliably heal himself from time to time to prolong the fight. You can also spam the bandit mercenaries on him to make things less of a hassle.

** The sound that plays when your instant-kill tower triggers their instant kill. Even moreso if it hits a GiantMook.

** Enemies with ranged attacks = Annoying micromanagement with moving rally points, [[ArtificialStupidity or the soldiers sit there and do nothing.]] [[GoddamnedBats Twilight Harassers]] actually ''take advantage of this'' by teleporting backwards out of your troops' range and firing a painful ranged burst damage attack.

** The second half of ''Vengeance's'' final level has King Denas' mortar troops dropping flaming TarAndFeathers on your towers to disable them. In order to free your tower, you either need to wait ''40'' seconds or pay 125 gold. Unlike Umbra's and the Spider Goddess' tower-destroying, this happens ''far'' more frequently. Better hope they didn't hit one of key importance, and if they did, better hope you didn't spend too much of it upgrading your stuff! Even worse, it lasts ''indefinitely until cleared'' in the Heroic and Iron Challenges, but it's thankfully reduced to 30 gold in the Iron Challenge.
** Snow Golems in the Frozen Nightmare expansion initially appear on several spots on the map including areas near your exit. They're dormant until a certain wave passes, after which they get up as a slow but powerful enemy with ''very'' high HP that drops a paltry 25 gold on defeat. To get rid of them prematurely you can pay a huge 200 gold to drop a bomb on their dormant bodies, which gives you a SadisticChoice: Spend a huge amount of gold, or fight an annoyingly tough enemy that drops chump change which can be spawned near your exit. Thankfully, the cost needed to bomb them is reduced to 100 gold in Heroic challenges, [[AntiFrustrationFeature and they do not appear in Iron Challenges at all]].

** "Ali Baba" requires your Assassins to pickpocket up to a whooping '''10000''' gold in total. At max upgrade, the upgrade only has a 40% chance to trigger while yielding only ''1-3'' gold per success. You can accelerate the process by building Assassin Guilds on nearly every available spot, but it is a very risky move as doing so [[CripplingOverspecialization will cripple your defences]] and possibly end your run early if not careful.
** "Let it bleed!" needs you to kill 100 enemies with bleed damage. Emphasis on the word ''kill'', meaning that you risk having your other towers land the killing blow if in range or even by normal attacks. This is only possible with Templars having the Arterial Strike upgrade and the hero Cronan who has a whip attack. You can do the same as stated above but you have to take note of the risks doing such an action.

* ThatOneAttack: In ''Vengeance'', we have the Anurian Chasers' [[InASingleBound leap attack]]. When they get within a rather generous distance to your troops, they perform a leap that not only [[DungeonBypass clears a good bit of the lane]], but the landing also deals a moderately damaging area ShockwaveStomp. The main reason why it's an attack you don't want to see is because they [[ZergRush appear in huge numbers]], and all of them using this can and ''will'' whittle down Barracks troops while easily sending the group of frogs forwards past a third to half of your towers. Worst of all, this attack has little-to-no cooldown and they can immediately hop to your next set of troops to bypass more area and plow through them.

** Umbra, the FinalBoss of ''Frontiers''. It seems like a standard FlunkyBoss at first, but when you "kill" it, it explodes into many small blobs which you must destroy as much of, because they'll reform into the boss (but its Maximum Health will be lower if you killed some of them). The battle only gets harder as it goes on as it then uses EyeBeams to outright ''destroy'' your towers (This is ''one of two enemies in the entire series'' that can do so), making it harder to kill his smaller Mooks. In order to beat him, you need to keep killing him and his blobs before he destroys your defences and his hordes get through.

** Maginia Shores from Vengeance is often seen as a ridiculous jump in difficulty from the main game, even by Elite Stage standards. You are just simply bum rushed by a horde of heavily armored enemies, but they each have their own tricks so you can't just pound them with magic (Chasers leap onto your troops to bypass your towers and Wardens have their shields replaced by Infusers). The waves involving Wardens and Infusers can get especially hairy, as the game chucks so many of them at once despite having very good armor.

** The Druid towers in ''Origins'' are considered rather useless due to having nothing to circumvent the ArtificialStupidity of the Artillery towers not to mention being unable to hit air units at all[[note]]In the original, Big Bertha has homing missiles while Tesla has the ChainLightning. In ''Frontiers'', DWAARP has a 360 degree splash damage while Battle mech has the afromented homing missiles. In ''Vengeance'', the Goblin Zeppelin can be positioned to affect troops effectively, the Melting Furnace uses a 360 degree splash, the Rotten Forest has a similar 360 degree area of effect In ''Origins'' both the level 4 druids uses the same inaccurate rock throw with only clobber as the reliable splash damage[[/note]] with the ''Burst Arrows'' being considered to be far more reliable splash damage than the Druids. This unfortunately has the side effect of making swarms that much more difficult compared to other games but particularly the spiders who are both fast and easily shrug off the splash damage from the ''Burst Arrows''.
** In a similar vein, the Goblin Rocket Riders in ''Vengeance'' are seen as one of the more useless towers. Like the Druid towers in ''Origins'', they share similar weaknesses but are even less reliable. Nitro Boosters are a nerfed version of the Dragonbreath or Wasp missiles, having much shorter range and inability to target air units. Minefield is unreliable due to random placement on the track and can outright miss enemies that don't go close to them. Finally, unlike ''Origins[='=]'' Druid towers that at least had abilities to stall or stun (Runed Bears and Clobber), Rocket Riders don't even have a way do either. The other artillery towers in the Melting Furnace, Rotten Forest and the Goblin War Zeppelin are seen to be more useful thanks to having wider, more reliable Area of Effects and stuns, or dealing more damage while being more versatile.
** The Templars in ''Frontiers'' are pretty universally agreed to be outclassed by the Assassins for most situations. Assassins have similar surivability (due to their dodge rate), way better damage, and their upgrades cost a lot less. Additionally, the Assassins go into stealth when not moving or in combat, so they can't be targeted by ranged attacks. The Templars' only real saving grace is using them against enemies with area-of-effect attacks, which the Assassins can't dodge.

* BreatherBoss: After 15 brutal waves in [[BrutalBonusLevel the Sunken Citadel]], Leviathan comes out as this. His extremely slow movement, lack of useful tricks (his only ability - stopping to disable certain towers next to the coast for a second - makes him stop while doing so) and weak minions (Greenfins, Deviltides, Redspines, the DemonicSpiders only appear if you take too long) make him pale in comparison to his own EliteMooks.

* GoddamnedBoss: [[spoiler: Vez'nan. He periodically casts a spell that renders a large number of your towers temporarily unusable (which is ''very'' annoying), and kills normal soldiers in one hit, but he doesn't have that much health.]]

** Lord Blackburn from the original is up there as one of the toughest bosses in the series. He has a very dangerous ability to temporarily stun your units and up to EIGHT towers within a ''massive'' range, deals heavy area damage making him hard to block even with Paladins, gets a rather short distance to your exit, has [[HeavilyArmoredMook 90% physical resistance]] (due to being a TinTyrant) which makes magic towers a must, and several of his flunkies are highly resistant to magic. Speaking of which, a number of his flunkies are [[GoddamnedBats annoying]] (Black Hags) or [[DemonicSpiders outright dangerous]] (Lycans, Fallen Knights), compounding things further.

* MostAnnoyingSound:
** The "Tak Tak Tak Tak" pickaxe sound that Quarry Workers make whenever they dig. It's loud, they dig very often and they appear in decent numbers, which means that waves containing them will play that sound a lot.
** The loud "Hoooaagh" sound that Troop Captains make when promoting Recruits into armored Footmen. Aside from now having to fight a stronger enemy, you'll be hearing it a lot since Troop Captains aren't exactly rare enemies and tend to spawn with Recruits.
** The "nyah nyah" sound the savage warriors and ghouls make whenever they cannibalize one of your troops.

** There's a pretty good reason why Mactans never fights you directly. She's only as big as a Son of Sarelgaz. While those are durable, armored and magically resistant, a single one isn't much trouble to defeat for a late-game defence. Thus, Mactans avoids direct combat with your towers as they would end her very quickly.