Boss Battles in video games can require a wide variety of strategies and tactics to defeat. However, how vulnerable they are to the player characters' attacks tends to vary from game to game. There are generally four types of boss vulnerability:
Always Vulnerable The boss is susceptible to damage at all times, and usually attacks relentlessly. This type can be difficult due to the fact that the player must concentrate on both avoiding the boss' attacks and hurting the boss at the same time.
Wait Them Out The boss cannot be harmed by any means until a certain amount of time has passed or a certain action is performed, at which point they will become vulnerable for a short period of time. This type can be easier due to the fact that you only have to concentrate on survival, and not have to balance offense and defense. However, it can be annoying if you miss the window of opportunity, since you will have to go through the attack pattern again before getting a chance at another shot.
Mixed A mix of the above. The boss is technically vulnerable at all times, but can become stunned or otherwise more susceptible to the player character's attacks. This may happen after a certain time has elapsed, or a special action or actions may be required.
- Most Role-Playing Games use this type by their very nature, though other types do crop up sometimes.
- Every boss in Iji is always vulnerable, except for Iosa's second form (wait it out) and the final boss (mixed). However, if you don't have any big guns, Proxima and the final boss become full Wait Them Out examples.
- Most bosses in the Kingdom Hearts series are either this or mixed.
- Most bosses in Hero Core.
- Ridley and Mother Brain in the Metroid games.
- Devil May Cry.
- Every boss in Eternal Daughter except for the final one, which must be waited out.
- The most common boss-type in the Mega Man (Classic) series. Almost every boss falls into this, and the ones that don't usually need to be waited out.
- The second phase of the fight with Skeldritch in The Legend of Zelda: Spirit Tracks.
- Both Omega Supreme's and Trypticon's first phase in Transformers: War for Cybertron. The former constantly attacks while you're trying to destroy all of his turrets, and the latter unleashes a near non-stop swath of destruction while the player has to time shooting power cells next to his weapon systems to overheat them.
- Most bosses in 2D Sonic the Hedgehog games are always vulnerable (with a few exceptions) but either can't be reached immediately, or are protected by their attacks. Usually it's not safe to try attacking, and is better to wait them out, but in some cases impatient gamers can exploit Mercy Invincibility to get all the hits in very quickly at the expense of their rings.
- In contrast to the other bosses, the lion-boar mammal in Chimera Beast is fully vulnerable.
- In Grief Syndrome, a Puella Magi Madoka Magica Beat 'em Up, most Witches blur the line, but fall on this side by being almost always attackable. Gertrud and Charlotte have jumping attacks which take them off the screen, but otherwise can always be hit. Kirsten switches places with her decoys fairly regularly, but can always be hit when she isn't in that animation. Elsa Maria goes underground to move, but comes right back up.
- Most bosses in Demon's Souls, Dark Souls (and its sequels), and Bloodborne work like this, though quite a few have spots where attacks will do more damage.
- The Blights and most overworld bosses in The Legend of Zelda: Breath of the Wild. Molduga is an exception to this though.
- Most of the bosses in Cuphead are like this.
Wait Them Out
- Hexen, where the Heresiarch casts a barrier spell that makes him invulnerable and reflects most attacks. While two classes have an attack that can pierce the barrier, Baratus (the fighter) does not.
- Most bosses in the Super Mario Bros. games.
- An Untitled Story.
- The Liquid Metal Processor and the final form of the Cruiser Tetron in Hero Core.
- Final Fantasy IV has the first boss, the Mist Dragon, which can only be attacked when it is not in its mist form (the game tells you this, after you get hit with a nasty ice attack, if you try).
- Final Fantasy XIII has a few bosses (and regular enemies) that are practically invulnerable until they are staggered.
- Most bosses in the Metroid games.
- The Cloud Child in The Spirit Engine 2 has a separate life bar that acts as a shield. Once you reduce it to zero, the cloud child will be stunned until the shield regenerates to full, during which you can attack its main life bar.
- Every boss in Lyle in Cube Sector, except for the semifinal one, which is always vulnerable.
- The Final Boss of Eternal Daughter.
- In Persona 4, Shadow Rise cannot be damaged, but halfway through the fight, she leaves and you end up fighting Shadow Teddie instead.
- Most bosses in the 3D Sonic the Hedgehog games, as well as those in the Sonic Rush series, though there are a few bosses that subvert it.
- Most in I Wanna Be the Guy, although some sections and bosses are Type 1. Thankfully, their vulnerable sections tend to be frequent.
- A few bosses in Mega Man fall into this category, notably ones that can fly out of your reach such as Gyro Man in Mega Man 5 (unless you have Gravity Hold).
- The Batomys in Valkyria Chronicles is only vulnerable the round immediately after it's fired its main cannon and exposes its radiators to cool down.
- Most bosses in the Legend of Zelda series are this, with most of the exceptions being in the first two games (and the aforementioned Skeldritch round 2), which are always vulnerable. Typically, you have to use the item you just got in the current dungeon to make the boss vulnerable to your sword.
- Both Omega Supreme and Trypticon's second phases in Transformers: War for Cybertron. For Omega Supreme, you need to stay alive until a power cell comes up from the ground, then corrupt it (and, thus, him) with Dark Energon before he can be hurt. With Trypticon, you need to wait out his bombardment and the Dark Energon parasites until Trypticon exposes the heat vents in his chest.
- Chimera Beast has three. The first boss (two lamprey things) are only vulnerable when they expose their heads to attack, the third (a Giant Flyer) can only be damaged when it opens its mouth to attack, and the fourth (an alien croc) can only be harmed when his head is out of the water and his mouth is open.
- In Grief Syndrome, the two hardest bosses get a bit of Fake Difficulty from this. Walpurgis Night has three phases most of the time (with a fourth Kaizo Trap phase before the final vulnerable phase), and she is only vulnerable during one of these phases. Oktavia von Sekendorf likes to pull a Doppelgänger Spin which makes her nigh-impossible to hit when she's not attacking, and fades into the background for one of her attacks.
- King K. Rool is often this in the Donkey Kong Country series, as are a few other bosses where you have to wait for barrels to be dropped first before you can attack. Boss Dumb Drum is this taken to its extreme; you don't actually attack him at all, you should wait out his attacks until he eventually explodes (except in the GBA version, where he just acts like other examples of this boss type).
- This is a fairly common setup for bosses in Super Mario World ROM hacks.
- Almost every boss in Brutal Mario works this way, to the point some hackers call such boss 'carol bosses', after the name of Brutal Mario's creator.
- Most bosses in the Scarlet Devil Mario series are like this, with the player having to wait until they generate a Goomba or Koopa to be able to hurt them.
- The final boss of ASPE Mario, some of the VIP series bosses, and most fights in Super Mario LD are also like this, with the player only being able to damage the boss when it drops a random throw block after every three or four attacks.
- Most bosses in the Kingdom Hearts series are either this or always vulnerable.
- The Final Boss of Iji is technically vulnerable to most of your weapons, though even the MPFB Devastator is not going to get you very far. The most effective way to injure him is to wait out his attacks until he uses a powerful Charged Attack, then reflect it back at him.
- Pinstripe Potoro in Crash Bandicoot (1996) is a mix. He's vulnerable at any point when not firing his gun (and technically vulnerable before then but you'd get torn to pieces trying), but only for the first three of six hits. For the last three, he becomes invincible, and you have to wait for his gun to jam.
- Corbenik in Project .hack. Despite having glitched/"infinite" HP, your attacks still deal normal damage. In reality, all three of its forms have 7000 HP. The second one will put up Ultimate Defense partway through the battle, which makes him invincible until the plot kicks in.
- Ghirahim from The Legend of Zelda: Skyward Sword. While he's not exactly immune to any of your attacks, he's a master swordsman and can easily block slow or sloppy attacks. You'll have to be smart about how you swing your Wiimote in order to get past his defenses. This gets subverted somewhat for your final battle with Ghirahim; the first phase is a Ring-Out Boss, while the second phase is type 2.
- In Viewtiful Joe, some bosses are vulnerable at all times (usually early bosses), some are only vulnerable after certain conditions (such as Fire Leo), and some are perpetually vulnerable but can be stunned for a longer combination of attacks.
- The final boss of Persona 3 FES: The Answer normally has a decent amount of defense, but after stopping its "Dark Embrace" attack, it will be unable to move for a turn. During this turn, it will take much more damage from anything.
- Shadow Warrior's bosses tend toward this. The glowing parts of their armor need to be hammered with gunfire until the Ki Line is exposed in order to destroy that part of the armor. Destroying all of the armor destroys the boss.
- Giygas in Cognitive Dissonance is technically Always Vulnerable, but has such astronomically high defense that even with the game allowing your attacks to actually reduce his HP (unlike in EarthBound Beginnings or EarthBound), it's functionally impossible to beat him with brute force alone. There are five ways to end the fight with some semblance of victory, all of which require the fight to progress to the point where Gieuge, the boss's previous form, goes One-Winged Angel, and which method is used determines the ending the player receives. Without spoiling any details of the endings, the ways to win are:
- Normal Ending: Lose to Giygas; progressing the battle this far is considered a sufficient victory by the plot, even though all of the protagonists die.
- Good Ending: Use PK Harmony to calm Giygas down and restore Gieuge, cutting the fight short without either side perishing.
- Secret Ending: Use Nightmare Empower to debuff Giygas's defense to manageable levels and whittle down his HP the old-fashioned way. This leads to an extra chapter instead of immediately ending the game.
- Paradox Ending: Use Song on Giygas, cutting the fight short and initiating an alternative boss fight which is Always Vulnerable.
- Joke Ending: Use the ballpeen hammer to ignore Giygas's defense stat entirely and whittle down his HP the old-fashioned way.
- GLaDOS in Portal, who is also a Puzzle Boss.
- Dark Cecil from Final Fantasy IV. Kind of a given, since it's the Trope Namer for Sheathe Your Sword.
- The tentacles in Half-Life. They are a Puzzle Boss immune to weapons that takes some running and turning on fuel and electricity to defeat.
- Same for the Gargantua, though it is vulnerable to explosives and energy weapons. The first time it is encountered though, the players arsenal is most likely insufficent to defeat it.
- Every Phase except Corbenik, which is mixed instead in Project .hack. The bosses take damage just fine their HP count is just glitched up, making them undefeatable. Data Draining them fixes this and also causes them to lose a lot of their special attacks, including their own Data Drain.
- A rather odd variation in Dark Chronicle: The True Final Boss, Dark Element, changes its color between red and blue every so often during your fight. When it's red, only Max can hurt it. When it's blue, only Monica can hurt it. Unfortunately, it's never vulnerable to the Ridepod or its Nova Cannon.
- The Grand Mother from Hero Core is a bit of an odd example. It's completely invincible until you destroy its flunkies a few times, at which point it goes berserk and loses its invincibility entirely.