YMMV / The Binding of Isaac

  • Alternate Character Interpretation: Even unseen characters are subject to this. To list:
    • Is Isaac a victim, a sacrifice, the spawn of the devil (possibly even the Anti Christ), or Messianic Archetype?
    • Is ??? Isaac post-suicide? Is he his own person?
    • Are the other playable characters alternate personalities? If not, are they related to Isaac? Is ??? one of them?
    • Is Mom a religious zealot, just insane, or both? Did she go insane from religion, raising Isaac, or her husband leaving them?
    • Is God evil or good in this game? Did He have Mom sacrifice Isaac for fun, as a test, or because he was the Anti Christ? Did He even ask her to do it or was she just imagining things? What is His relation to the Angels?
    • Is Satan trying to protect Isaac or awaken him as the Anti Christ? Does he just see Isaac as a customer and tries to get more payment in the Sheol path? How is he related to Mega Satan?
    • Did Isaac's Dad leave because he was a Jerkass, didn't feel like he could be a good family man, or to get away from his mentally unstable wife, who may have had several miscarriages?
    • Is the ending where Isaac turns into a demon good or bad? Is Isaac finally happy?
  • Anti-Climax Boss:
    • Mom's Heart/It Lives will rarely pose a serious threat to anyone who is good enough to reach it. It is considerably more of a challenge in Rebirth, however.
    • The red champion version of Mom looks impressive, but is actually far easier to beat due to her greater attack speed and lack of Mook Maker abilities. Players can just dodge the telegraphed foot attack and retaliate, occasionally dodging a bullet spread from her eye.
    • Satan in Rebirth. While his fellow Final Bosses received new tricks which generally made them much more impressive than they were in the original game, Satan stayed more or less the same, with only a couple of new attacks added in only one of his phases, which are quite similar to the attacks he already had. Add the increased potential for powerful item combinations, and he just Can't Catch Up.
    • Ultra Greed in Afterbirth is undeniably a fun battle, and it does take a while to win thanks to his scaled health gimmick. That said, given how easy it is to collect powerful items over the course of the run, coupled with the fact that Ultra Greed's attacks are telegraphed well in advance, he'll only pose a real challenge to characters with low health (i.e. the Lost) or those with low speed attacks. A patch buffed the health of his giant coins, making them more likely to survive the player's attacks, which means he gets to summon more mooks and recover more health (not to mention the bombs, though those are the easiest to dodge). He also Turns Red as his health drops, making the fight much more challenging.
  • Author's Saving Throw:
    • Edmund admitted that The Lost was infamously too hard to play, and he has received a major buff in Afterbirth: he now has spectral tears, letting him fire through obstacles, and he starts with the D4, allowing him to reroll all his items in the hopes of getting better ones. A later patch buffed him even further: Holy Mantle is now an unlockable starting item for him, which many players consider to be THE most valuable item to get as the Lost, as it turns him into a two-hit wonder rather than one-hit. Although this clashes with the D4 if you have both since starting with one of the most powerful items for the Lost means there are very few rolls you could get that would overall improve your load out.
    • After some rather major internet outrage accusing Edmund of not caring about the fanbase and "throwing a temper tantrum" due to a patch adding extra items in that were promised to be put in the game in the first place, Edmund made this post, elaborating that the items weren't originally in the game due to an unexpected glitch, and he meant no ill-will towards anyone in the community.
    • The Afterbirth Alternate Reality Game was an example of this. In Rebirth, Edmund wanted the community to work together to unlock something in the game, but in the end, it was data-mined. In Afterbirth, the unlockable content wasn't even patched in until the game was finished.
    • After some backlash concerning nerfing the Stopwatch, Edmund tweeted asking the community what items they would like to see buffed. As of December 6th, a patch buffed several bad items (for example, the Scissors are now a two room charge, the Friendly Ball is now a three room charge, and the most important of all, the Stopwatch is no longer a Special Item, and activates when the Holy Mantle is triggered), fixed several bugs, and finally reworked sacrifice rooms.
  • Best Boss Ever:
    • Loki, an always-smiling demonic baby, is quite preferred over Monstro II as the boss of the fifth floor. They even call him "Mr. Cool" in the credits.
    • Satan, boss of Sheol, is the most complex boss fight in the original game and is the only boss to have multiple complete health bars. Before he even lets you fight him, he sends out one of The Fallen at you, and once you beat him, he breaks out of the statue and goes berserk, using updated versions of The Fallen's attacks. And after you beat him... he gets right back up, flies offscreen, and uses Mom's battle strategy as the fight becomes more fast-paced with him constantly stomping on the floor. After you beat him here, he finally falls and gives you Ending 11.
    • Rebirth naturally tops Satan with Mega Satan, who combines Giant Hands of Doom, mixes in minor elements of Bullet Hell, and summons at least thirteen Degraded Bosses with a grand total of eleven phases. And then he still has one more form left, where he goes all out with the Bullet Hell in a last-ditch effort to kill you.
    • Afterbirth's Ultra Greed due to having a unique gimmick involving coins that, if not destroyed, can unlock doors that summon enemies, and Hush due to being the game's biggest example of Bullet Hell but this time in a 2x2 room. Both also have an increasing max health depending on the damage you're doing, so even if you're on the most powerful run of your life, they still won't become a one-shottable Anti-Climax Boss.
  • Breather Boss:
    • War's first phase is exactly what you would expect having seen Pestilence and Famine, with no summons but more aggressive attacks. His second form... is basically a quicker Lust but saddled with Gemini's poor running stamina, far too late in the game to be very intimidating for anyone with speed upgrades.
    • The bosses which spawn in the Brutal Bonus Level are noticeably less difficult than earlier bosses. Harbingers also tend to be nerfed to second stage only. Not so, however, in the TRUE Brutal Bonus Level, which can quite frequently feature any Harbinger (even Death is normally fought only three levels ago) in a room far more restrictive than the one you normally fight them in. They're not nerfed, either; they're exactly the same as the actual boss fight.
    • Pride's diagonal tentacle/shout attack probably won't hit you if you're firing at him with your tears, and his bombs are for the most part easy to avoid.
    • Lust is a Bullfight Boss set up in an arena with rocks to slow her charges. Unless your character is very slow, she's incredibly easy to beat even in the opening level. Her upgraded version leaves a damaging trail of blood, but it tends to fade by the time you circle around.
    • Wrath is one of the few bosses who's more of a threat to himself than he is to you. He's not very quick-moving and his only means of attack is to spawn bombs — bombs which he's not immune to. Using them against him is easy.
    • Scolex was formerly this. It's only fought in Womb I, but due to its very low health pool, it's fairly easy to defeat. It was buffed in Wrath of the Lamb, but it's still easier than other Womb I bosses like Lokii (the second version of Loki in which Loki is split in half) and Death.
    • Gemini and its variant Steven are, even in spite of the others having additional tricks, incredibly easy to beat. As long as your character isn't lacking in speed, they can't catch you and their bullets usually won't hit you. (Ironically, Blighted Ovum, the third variant, is one of the hardest bosses in the game).
    • Pin the worm is borderline impossible to get hit by once you've locked down his pattern. Hanging out on the bottom of the screen causes his bullets to miss every time if you aren't in the path of the head. In Wrath of the Lamb, Pin can be wiped out with one Bomb, absolutely fries to piercing attacks, and can bomb itself with his own ipecac shots. Rebirth fixes these weaknesses, making Pin not a total pushover, but the original strategy is still viable.
    • The green champion version of Gurdy, while still high on health, doesn't shoot bullets, instead preferring to spawn flies. This makes it much easier to avoid her attacks.
    • Gish is essentially a reskinned Monstro that fires a single slow-moving explosive and spawns enemies that only fire diagonally. Players skilled enough to unlock him will most likely never take a hit to him, and he drops Little Gish, a familiar that shoots useful slowing tears.
    • From Rebirth is Mr. Fred. This is a boss that is fought in the Womb, but is completely immobile, is assisted by fairly non-threatening mooks, and his 4-way blood creep bullets can be nullified by flying or shielded tears. Depending on the room layout and player upgrades, it may be possible to kill the boss from a position where none of his bullets will even reach Isaac.
    • Poor Daddy Long Legs. Not only is he one of the rarest bosses to find in the game, but he actually has much lower HP than the other bosses in his floor. His attacks are fairly telegraphed and easy to dodge as well, as long as you don't stand still. Triachnid, his alternative version, is rarer and even easier because he only has three legs to attack with. Keep in mind that both of these bosses are in the Womb, one of the more difficult levels in the game.
    • Larry Jr. is a breeze to fight, since he/they don't target you, but simply move around at random. Just as long as you stay out of his path and don't let yourself get cornered by poops, killing him without taking any damage is pretty straightforward.
    • Loki is far easier than many other bosses in The Depths, with his only attacks being a small number of unaimed, easily avoided bullets and summoning a Boom Fly that can be used against him. His boss room does come with a single moving spiked block, but otherwise he's pretty easy.
    • Afterbirth brought in an influx of rather challenging boss encounters... and then there's Little Horn. Despite his demonic appearance, his only marginally-dangerous attack involves summoning pits for you to fall into, which are easily dodged and completely ineffectual if you're flying. His only other projectile is a slow-moving over-sized homing tear that can be destroyed with repeated fire, and his penchant for teleporting and summoning bombs often leads to him blowing himself up in a similar manner to the above-mentioned Pin. If your speed is even slightly decent, it's unlikely Little Horn will even manage a hit on you.
    • On the topic of Afterbirth, there's The Forsaken. Don't let his similar appearance to The Haunt fool you - his only major attacks involve summoning a single Bony and firing a spinning tri-shot Brimstone laser, which sounds menacing in theory but in practice is actually much easier to dodge than expected. On top of his limited arsenal, he has an absolutely pitiful amount of health and is not nearly as mobile as his successor.
  • Breather Level: Even during the Brutal Bonus Level, there will occasionally be rooms with only a fly or a pair of helpless grubs, which still recharge your special item and have a chance to drop items. There will also always be some empty rooms, and it's possible to spend quite a long time in the arcade with virtually no chance of death.
  • Broken Base:
    • Rebirth caused one initially from fans who didn't like the idea of rereleasing the game instead of getting more content and drastically changing the art style, but this one died off pretty quickly when Edmund mentioned that because BoI was made in flash, the game simply couldn't handle more content being added while still functioning. The trailers and screenshots that have shown the new synergy between items that formerly had none (like Loki's Horns + Mom's Knife) has silenced the detractors even further.
    • The super secret in Rebirth, The Lost, a Hidden Character. Hoo boy. What happened is that the game's creator put in a riddle that he anticipated would take months or even years for the whole community to solve. It was actually cracked in the week following the game's release, with the aid of people extracting data from the game's files and executablenote . This prompted the creator to angrily admonish the fans for ruining the riddle and announce that there will be no more such secrets in future expansions to Rebirth. There are many ways people are split over this:
      • Was the creator's reaction justified? He and the developers put lots of effort to ensure that the riddle would not be solved accidentally, but still accessible with the hints delivered in-game, and would be a fun experience for people to solve together. People then circumvented all that and just read the solution from the files. Or perhaps the backlash was childish, punishing the whole community for the deeds of a single data miner (with whom most of the fans were angry as well). Besides, the creator has grossly overestimated the time it would take for a huge fanbase to solve the riddle together, despite this happening time and time again in Alternate Reality Games.
      • How much the spoilers extracted from files actually helped solve the riddle. The general consensus seems to be that the riddle was already about 80% solved and would have been solved anyway in a couple of days at most, since the community had all the pieces and just needed to put them together. But there are claims that people only started getting hints after the first detail (that the solution has something to do with dying in a certain way) was discovered by looking at the game files. And regardless of that, some people say that the community circumvented most of the riddle anyway, since they were using cheats to immediately test out various circumstances instead of waiting for them to happen naturally in the game as was intended.
      • It's highly controversial that the creator, despite wanting it to be an elusive secret, made unlocking it into an achievement. A secret achievement, but there are legitimate ways of looking at those on pretty much all of the game's distribution platforms. And not only that, but there are other achievements, and even in-game items, that require unlocking the super secret. At this point, people who were not interested in the riddle but just wanted to have 100% completion decided that anything goes, which might have prompted the data mining.
      • Some say that it's a good thing that the creator will not be putting any more secrets like this into his games, because it was a poorly designed mess. It required way too much effort to be solved by any one person, so people not interested in the community (and this is primarily a single player game) or just left out of the loop at the exact time where fandom was working on the riddle would have no way of unlocking the secret (and any further items) other than just looking up the answer online. And there's the fact that while putting together clues may be fun, the unlocking itself requires a lot of time even if one knows all the steps and is a painfully boring, RNG-dependent grind that requires dying to certain enemies with certain characters in certain order (and dying in any but the right way will reset the sequence), which is completely unnatural and simply not a fun way to play the game.
      • The Lost unlocking requirement was changed; all you have to do is hold a Missing Poster and die in a sacrificial room so you resurrect as The Lost. Needless to say, a lot of people are happy they changed the method, while others are pissed because now you can play with other characters, get super strong, and intentionally become The Lost before fighting the achievement-unlocking bosses, making the entire challenge of playing with him pointless. Either way, nobody likes how the devs did such a huge change without warning the players.
    • The soundtracks, good grief, the soundtracks. Some people like the electronic songs of the original + Wrath of the Lamb better. Some people like the darker ambiance of Rebirth. Although one thing that's near-universally agreed on is that Rebirth's theme for The Chest, "Sketches of Pain" is awesome (especially since the theme in the original was just the normal boss theme.)
    • Afterbirth got hit with a double whammy on November 4, 2015:
      • On that day, a patch was released that severely nerfed Azazel and Lilith, more than halving the range and damage of the former's Brimstone laser, and doubling the recharge time of the latter's Box of Friends — although Edmund has since admitted that the Azazel nerf was a bit too harsh.
      • The reveal that the patch added in new items that were supposed to already be ready at launch also caused some major outrage. Due to the fact that this patch went live exactly 109 hours after release, which was exactly the amount of time it took dataminers to unlock The Lost and the maximum value you can reach on the Greed mode donation machine, a fair few people believe that this is a form of petty revenge on Ed's part against the dataminers that he's taking out on the entire community, although Edmund has since stated that he has no ill-will towards the dataminers and that the items were missing due to an odd bug that he hadn't realized until a few days before the patch.
      • And the game still doesn't have all the 120 new items after the 11/04 patch. Is Edmund lying about it to cover his "revenge"? Is the DLC simply not completed yet he released it anyways just to get Halloween sales while patching the missing content in and pretending an ARG is in effect to try and cover this up? Or is it really a bug and people should calm down since that kind of thing is normal during game release? He said "We weren't aware of the missing items" and that the bug happened due to "a thing" he can't talk about.
      • Edmund confirmed on Twitter that the ARG is officially over and the full DLC is in game, the +120 items include the trinkets and co-op babies. Depending on who you ask, the ARG was either very fun, Edmund did a great job and the DLC is great, or the ARG was poorly done since many people didn't care, Edmund is an egoist for having locked content out for people that had nothing to do with this, and the DLC was underwhelming.
    • Greed Mode, especially as of its post-patch post-ARG incarnation, rubs quite a few people the wrong way.
      • To start, a lot of content is locked behind the "Greed Machine" found after completing any Greed Mode run. In order to unlock everything, including what was "unlocked" by the ARG, the player must donate a whopping 1,000 pennies to the machine. While that would be about 10 runs or so, the machine has a chance to jam every time you put a penny in. For every five cents you've donated total, the chance to jam increases by one percent, and each character has their own percentage. While the intent seems to have been to encourage switching characters, in practice it just lengthens what was already an unfun grinding experience. What makes it worse is that the only real "breaking" method is to use the Glowing Hourglass to constantly reset the fight so the player can donate... one cent. Without a Chaos Card, the player will have to fight Ultra Greed, an incredibly long fight, for hours. Greed Mode is seen as either a fun diversion, or a horribly balanced inclusion into the game. A recent update rebalanced the jamming mechanic, causing the percentage to rise much slower than before. Needless to say, there has been less criticism as of late.
      • Greed Mode's final boss, Ultra Greed. His main gimmicks are his scaling health and dropping coins that affect the fight in various ways. While most people agree the concept is very fun, some people find his fight incredibly tedious, especially when you have to repeat it so many times. One patch gave him a ridiculous buff, doubling the health of the coins, and ramping up his health to an absurd degree, to the point where a character can be too powerful to ''damage'' him. Even after he was toned back down, fans were not pleased to find out that one of the donation rewards is "Everything is Harder 2", which buffs him again, and is very low on the list of donation rewards.
    • The Stopwatch nerf — instead of permanently slowing everything down, it now procs on taking damage and the slowdown effect lasts for a single room. It's either a welcome change to an instant-win pick-up, or a pointless alteration turning an item that takes time and effort to unlock into something not worth bothering with. Additionally, it was still in the "special item" pool for a while post-nerf, which meant seeing it lowered the likelihood of getting another OP item. The outrage has died down a bit now that the Stopwatch is no longer a special item, and also triggers upon activating Holy Mantle.
    • Item nerfing in general. Is it welcome to help balance the game, or is it unnecessary in a singleplayer game with no meta?
  • Crosses the Line Twice: Literally all of the humor qualifies. The best example is probably the infamous "Yay, cancer!" — a description of a trinket that's literally a tumor and increases the rate of fire.
  • Demonic Spiders:
    • Leapers, the bane of any player going for a No Damage Run (or playing The Lost). Their erratic jumping makes them hard to hit consistently, they can jump to any part of the screen with little warning, and when there's four of them, the screen tends to be filled with bullet spam from repeated jumps. A real pain to deal with.
    • Mr. Maws. They swing their head at the player, which can be very hard to dodge, and upon death, they leave shooting heads (and sometimes slow-moving bodies) behind which can be a problem of their own. Even bombs and Brimstone (unless buffed with extreme damage) won't get the head on the first hit. They can be the utter bane of people going for No-Hit runs, because there's one room configuration that they are practically impossible to dodge as you enter.
    • Psychic Maws. They're a variant of Maws, which are already annoying enemies. These fire homing tears, have increased health, and have an Eternal Fly circling around them which can block hits. Fortunately, they are rather rare.
    • Knights have a rock-solid front end that shrugs off almost all attacks. Its weak point is the exposed brain on its back, but good luck getting a clear shot at it, since they have a tendency to turn around and run right into you after you position yourself behind it. To make matters worse, there's a version of this enemy with Isaac's face in place of the brain which charges at you at full speed.
    • Eyes, especially when they're not located in the center. These are likely to hit the player. The bloodstream versions are even more dangerous (especially without having a weapon to shoot over rocks), as bloodstreams last longer than Eye Beams and they're often situated between rocks, making it hard to hit them.
    • Clotties, when in groups or in certain room layouts. They move around haphazardly, fire in all four cardinal directions at once (which forces you to either put yourself in danger to hit them every time or use unreliable diagonal shooting, which may not always be viable in certain layouts), and do so at completely random intervals (i.e. not guaranteeing you'll even have enough time to try to hit them) with next to no warning. Even worse are I.Blobs, the white "Alternate" varieties that do 8-way shots, making even diagonal shooting dangerous. Fortunately, these are extremely rare, but if you are unlucky enough to see one in a floor, expect to take some damage.
    • Wrath of the Lamb has the jumping spiders known as Trites. They're just like hoppers, except they move at nearly double speed, take more hits, and often come in packs of 4 or more.
    • Chubbers. They have the same appearance as a Vis (the walking stomachs that shoot giant lasers at you) but have a small Chub housed inside each of their bodies, which fires rapidly, can go through rocks and walls, and takes out a whole heart of health. It doesn't help that they have an insane amount of HP and often come in packs of 5 or 6. Made even worse in Rebirth: their Chub now blocks tears!
    • Keepers. They're the little bouncing Greed heads. They jump around erratically like Leapers, put you through Bullet Hell, and every single shot or collision with them makes you drop coins, making one lost forever. Much like spiders, they have the uncanny ability to squeeze between boulders and pits joined by one corner. They often come in packs of four, and Super Greed is all about spawning these.
    • Hangers, which are basically hostile shopkeepers. They fire three way shots, have Eternal Flies circling them, and have a ton of health.
    • Masks and Hearts. The mask is invincible, and is connected to a heart which can soak a lot of damage. The masks charge and have very good reflexes. The hearts try to flee from Isaac, and if he gets too close, fire four shots in the cardinal directions (like the Clotties) to defend themselves. Fighting them in rooms with rocks makes them even harder to deal with. Finally, they are rarely alone. Good luck dodging the extremely nimble masks while trying to get a clear shot at the hearts, which retaliate on their own accord.
    • And, well, basically every enemy in the Womb and Beyond, since they do one heart per hit instead of half.
    • The new wall-crawling spiders in Rebirth. They come in three flavours: three-shot burst, triple shot, and Brimstone. The three-shot burst version is annoying but easy enough to kill. The triple shot one is blind, fires without warning, and moves random. Rooms can potentially have three of them stacked on one side, making it difficult to kill them without taking damage. Rooms with the Brimstone variety often have you taking damage immediately as you enter the room, sometimes twice from the same Brimstone laser.
    • The Walking Hosts. These enemies are much harder to coax out of their shell while they slowly walk to you, and often come in rooms where it's tricky to maneuver around. The 2x2 room containing four of these enemies and the perma-firing Grimaces is one of the most notorious rooms in the Caves.
    • In Greed Mode, any enemy that likes to teleport/tunnel around the room (such as Lumps, Round Worms, and Wizoobs). The double-sized room makes these enemies much harder to track down and kill, which means that they'll often be still alive when the next wave spawns, essentially making you deal with two waves of enemies at a time. And if the Random Number God sees fit to saddle you with multiple waves of these guys in a row, good luck.
    • Afterbirth added a skeletal version of Mom's hand which is approximately 100 times worse than the original. The original just flew down and tried to grab you. This one does the same, only when it lands, it releases an earth wave like The Cage, and when it dies it releases spiders.
    • Afterbirth also gives us the Imp, which is basically what you get if you take a Baby, give it more health, make it actively try to dodge your shots, and make it shoot five times in a row. To top it off, these guys love to hang out in Devil Rooms, hiding behind the statue to get cheap shots on you before you fully register that it's there.
  • Disappointing Last Level: Compared to the Halloween Update's Sheol, which tested your skills with the base game's items and had an awesome boss at the end, Wrath of the Lamb's Cathedral, which further tested your skills and had a brutal boss at the end, and a later update's Chest, which essentially starts out with four Item Rooms and contains mostly bosses, Rebirth gives us the Dark Room, meant to be the demonic counterpart to the Chest. It succeeds in all the wrong ways, with the level starting out with four Red Chests instead of trading four keys for four items and having much more unfair rooms. Its only redeeming counterparts are a great boss fight at the end and the fact that non-Red chests still pay out with items.
  • Ear Worm: Try finding a player that doesn't have Sacrificial stuck in their head. There's also the 8-bit version that plays in Arcades, which might be even catchier.
  • Ensemble Darkhorse: The Dark Bum from Rebirth quickly became one of the most wanted items. When it was severely nerfed, there was fan outcry for him.
    • Sissy Longlegs, while not a very powerful item, is cute in her own way. Her description "she loves you" tends to give her a free pass on rerolls.
    • Bumbo from Afterbirth has won a lot of fans over with his array of rather useful abilities. The fact that he grows by collecting money, which tends to be rather useless later on, also helps. Edmund seems to have been very aware of his popularity, as he is now receiving his own Spin-Off game.
    • Dry Baby is also considered a god-like item due to its ability to block pretty much all shots and damaging every enemy in the room each few shots it blocks.
  • Fandom Berserk Button: Using the Flash Filter in Rebirth will often get people to mock you for it, particularly those who use 4chan. This is most likely because of how blurry the filter looks compared to the non-filtered game, and the fact that the filter was only added in as a joke against the people who hated the pixel-art style of the game.
  • Fan Nickname: Mega Stan for Mega Satan.
  • Game Breaker: Has a separate page.
  • Genius Bonus:
    • When under the effects of Whore of Babylon, your character leaves a small puddle of blood rather than the usual puddle of pee left at low health every time you enter a room. This may be a reference to past conceptions of what periods were (a curse due to Eve's actions of original sin) or even to the Biblical passage introducing the Whore of Babylon, "...and I saw a woman sit upon a scarlet coloured beast..."
    • Azazel is a fairly commonly referenced demonic name. But it's also a word for a sacrificial scapegoat — Azazel, like Isaac himself, is named after a sacrifice.
  • Goddamned Bats:
    • Knights and their many variants are hard to hit, since they're invulnerable in the front and have unpredictable movement patterns. Some even turn to charge you. Past a certain point, piercing is practically required to survive. It certainly doesn't help that there's a boss version.
    • Hosts take cover and shoot 3-way shots. Sometimes weird maneuvers must be taken for them to show up. There is a red host variation which cannot take cover, but it shoots a 5-way spreadshot and fires more often.
    • The many varieties of flies fit the trope better. Especially the ones that shoot at you, or explode in a flurry of bullets upon death.
    • Similar to the flies, the many variants of spiders fit this as well. Not that hard to kill (once you learn the basics of dodging), but they are on every floor, many bosses and some mooks spawn them, and they are just random enough in movement to chip damage you to death over the course of a long run. Good luck trying to kill them with the Ipecac or Fetus in a Jar.
    • Lil Haunt, the mook version of The Haunt, is an extremely cheap enemy. Their movement pattern is designed to lead you, which makes it very easy for them to corner you (but also extremely easy to control them if you know this). They have a bullet attack which has no tell or consistency. They are tougher than most mooks their size. Finally, they make the boss fight against The Haunt that much more annoying.
    • Wizoobs, the ghost enemies that spend most of their time phased out of existence except to spray a hail of bullets in your face. Their attack isn't too hard to dodge, but they have a boatload of health, don't stay tangible long enough for you to deal any meaningful damage, and tend to spawn in packs of six or more. No matter what items you have, they will take a disproportionately long time to kill. Afterbirth adds in Wizoobs which shoot Brimstone to the mix, only making their infamy worse.
    • Bonies. Not terribly dangerous or tough, but their bone throw has absolutely no tell, and they will use it almost without fail if you try to line up with them to take a shot, making it very likely that one of them will hit. They're also some of the few enemies that Azazel has trouble dealing with, as his short range is pretty much an invitation for a point-blank bone to the face.
    • By the time you reach Chapter 6: Headless Horseman Heads. Their size, speed, and health make them take a while to kill (unless you're ridiculously overpowered), they fire three-way blood shots, and they often spawn in groups of two or three, or are accompanied by either Demonic or Holy Leeches. By this point in the game they aren't really that dangerous, but they're certainly annoying to fight through.
    • Fat Bats are both a literal and a metaphorical example of this. They come with a boatload of health, have unpredictable bullet attacks with no tell, and try to avoid your shots. On the other hand, they're also slow and don't shoot very often (and when they do, it's relatively simple to dodge). As a result, they're not exactly dangerous so much as tedious to fight.
  • Goddamned Boss:
    • Just mention Greed to anyone who's played this a few times and watch their blood boil. It's not just the fact that he's very hard to fight without being hit once (his attacks are completely random and have no tell whatsoever), but his appearance results in you losing the shop or secret room of that level. This can be annoying at best (meaning you've lost a key or bomb to get in for nothing), or utterly fatal (You so needed that shop for health...). The exception is when not having enough money, as Greed drops a lot of coins. And then, when you DO need coins, the game spawns a shop instead.
      • And just because the developers love to see us cry, they've given us a hardmode version of him, with much wider bulletspray (though it also means he can't hit you from the front), more health, and he spawns Greed heads.
      • Of course, if you have the D6 and are good at dodging, getting Greed in a secret room with the ability to enter over and over can lead to Greed farming. Add in the Habit and you have yourself a recipe to get every item in the secret room pool from one boss! That being said... Goddamned Greed!
      • Greed's infamy as a boss extends to Afterbirth by giving him a game mode of his own. In fact, a much harder version of him appears as the mode's final boss.
    • The other infamously annoying Sin is Envy. While he has the same chance of spawning as the Sins other than Greed/Super Greed, Envy takes the cake for not being difficult to fight, just tedious, especially when encountered on the first or second floor. He's an Asteroids Monster that splits in two (three as Super Envy) each time he's killed. He never attacks, just bounces around the room diagonally. And to top it off, while the other Sins drop potentially useful pickups on death, Envy leaves behind a Troll Bomb. While not particularly tough, the fight takes forever if you have no damage upgrades, to the point where many players will just reboot a run right then and there rather than put up with it. No wonder he has a constant Troll Face on him.
    • The green variation of The Duke of Flies when not having any bombs or piercing shots. The Duke spawns Moters which can be dangerous if shot, and it's hard to get a hit on him. For that matter, any variation of the Duke of Flies can be this. He's one of the easiest bosses to beat with powerups. Unfortunately, he's always going to be either the first or second boss in the game when he appears, which makes trying to shoot through his fly mooks extremely annoying. In fact, when you later see him as a Degraded Boss in the Womb or Sheol, it often turns into a Curb-Stomp Battle in your favor.
    • Monstro and Monstro II, for some. While their attacks are moderately dangerous (comparatively to the rest of thr bosses), they have easily the most health out of all the bosses for their respective levels, making the fight boring and thus, prone to mistakes. They can also render themselves immune to most attacks just by jumping (which they'll be doing constantly), making it hard to hit them with bombs or certain pick-ups.
    • The Krampus. Just by appearing, he will invalidate any Devil Room you might have earned on the level. He also loves to appear early and takes forever to kill. His double burst fire attack is very difficult to avoid, even if you are running circles around him, and his cross blood attack has an incredibly short tell. Furthermore, the coal item he drops is of questionable value, as it requires Brimstone or high range to be truly effective. It doesn't help that Afterbirth gave him the ability to rotate his Brimstone beams, which makes it even harder to avoid and can potentially result in taking damage twice from the same attack.
      • If you have the D6, the coal item can be rerolled for a random Devil Room item that you can then pick up for free, making the fight much more worthwhile.
      • In Rebirth, he drops the much more useful Head of Krampus, an item that unleashes a very powerful four way brimstone shot that can clear rooms easily and do serious damage to bosses. It ended up being so powerful that version 1.031 nerfed it from a three room charge to a six room charge.
    • The Mask of Infamy, if you lack a piercing attack (which you usually do). In her second form, she's pretty much a knight with near-perfect AI, meaning she'll chase you around the arena in circles and occasionally one or two tears will land on her backside by luck and actually damage her. You could probably try using a bomb or two, yeah, but she's constantly moving and you can't just plop one directly in front of her. By design or by bug, she is also the only boss lacking a health bar in the original/WOTL version, which makes the fight much more infuriating.
    • The Bloat. He's a harder version of Peep and starts with both of his eyes out of his sockets. What's more is that if you stand right in front or to the sides of him, he will fire blood beams with next to no indication of doing so. If you enter from any direction other than the top, this can happen as soon as you enter the room, so unless you have high speed and godlike reflexes, you will get hit. The only mercy is that his bloodbeams can't shoot up, but then he may just leap to the top of the room and crowd you out.
    • Mom can be this, especially to less experienced players. Dealing with the many mooks she can summon while dodging her stomps at the same time can prove to be a very difficult task. It gets worse when she summons Clotties, Maws, and other projectile-using mooks. It doesn't help that rocks block the corners of the room and the doors have a chance of summoning her very fast and hard-to-dodge hand, leaving you with very little room to deal with your assailants. She's even worse in Rebirth, since the stomps come out faster and the shadows warning of them are much harder to see.
    • Rebirth brings out The Haunt, a ghostly spectre and his three familiars. As mentioned below, the familiars are very hard to fight without getting hit, he's a Cellar boss, and he has one of the highest HP totals for that point in the game, meaning you likely won't have enough power to give him a fair fight. Plus the fact that you can fight two of him at once in some rooms. Feel free to keep your hand hovering over the "R" key before entering the boss room...
    • Rebirth also adds Dingle, a living poop monster which is Gurdy Jr.'s annoying cousin. In addition to possessing the same triple charge combo as Gurdy, he also has a bullet attack and spawns mooks. On early floors when your speed is low, there's a good chance one of his charges may connect.
    • Little Horn from Afterbirth. His attacks aren't terribly dangerous and he doesn't have too much HP, but the problem is that he never holds still. Much of the fight has you chasing him and dealing chip damage as he teleports around the room dropping Troll Bombs and firing giant homing tears, praying that he kills himself by teleporting into one. Finally, he's a Basement boss, meaning that you're unlikely to have any good items to speed up the process.
    • Afterbirth also introduces Rag Man. While he's not an especially difficult boss to fight, since his only direct attack is a line of five homing bullets with short range, he has a disproportionately large amount of health for such a small boss, which makes the fight unbearably tedious. Every so often, he'll detach his head and roll it. If you don't destroy the head, which isn't easy because it can take a lot of punishment, it spawns a Ragling, a Trite variant which is tougher and shoots homing bullets. But that's not all. The Raglings leave behind bandages when you kill them. If enough bandages accumulate, Rag Man can instantly resurrect two or three Raglings, and heal himself in the process. The best part? Like the Haunt, he can potentially be the first boss you face, as he appears in the Burning Basement. It's even worse in Greed Mode, where you might end up fighting two at once on the first floor.
    • Scolex. He behaves similarly to Pin and is about as dangerous as that implies, except that only his tail segment is vulnerable. As a result, you generally only get a window of about a second or so to damage him every time he jumps, meaning that the fight usually drags on for far longer than it has to. Fortunately, he has one attack that leaves the tail vulnerable for a rather long time, but A.I. Roulette means there's no guarantee of him actually using it.
  • Good Bad Bugs:
    • After the Halloween Update, the Mr. Boom item's recharge bar got permanently stuck on full charge. That equals to an infinite supply of super-bombs! This one was fixed in the bugfix that quickly followed the Halloween update.
    • There was a bug where ??? gained complete invincibility when he took a Full Health Pill. This invincibility would last until he picked up an item that would increase the maximum health of a normal character. It even counted for No Damage achievements. Eventually, it was patched out.
    • As explained above, the Brimstone + Chocolate Milk combo was originally this, allowing you to spam blood beams all across the room for no charge delay whatsoever. However, this was quickly fixed for being too overpowered, and the resulting combo produced from it is now... less than satisfactory.
      • A bug that is not patched out, though, is the infamous Brimsnap glitch (named after the Lets Player bisnap)): if you keeping tapping the button while firing the Brimstone beam, it will potentially double its damage and increase its area of effect.
    • Defeating the Headless Horseman will sometimes unlock Little Chad and the connected achievement, even if you haven't cleared the Caves enough times to even unlock Chad himself.
    • On the less spectacular but more exploitable end of the scale, if you use the Temperance card to create a blood donation machine right next to one that was already there, you can use the mercy invincibility from touching one to activate the other without taking damage, doubling the rate of payout per heart. This could be extended even further if you find multiple Temperance cards on one level.
    • Wrath's bombs are treated as player bombs in order to make them pushable. This means that certain powerups which alter player bombs also affect his. Such as the Bobby Bomb powerup, which makes your bombs move towards the nearest enemy. The result is a hilarious easy win.
    • Before it was patched, when using Lemon Mishap after defeating a boss and leaving the room through the door, re-entering the room would allow you to fight him again, earning you an extra item.
      • A similar glitch that is currently not patched is that using a Portable Slot in a boss room after the boss is defeated, and getting a fly to buzz around the room. If you leave without killing it, the room will reset, allowing you to fight the boss again and get its item. This also works for other rooms such as secret rooms.
    • Before it was patched, the final boss fight against Isaac himself bugged out and had no music at all. This made it way more dramatic than the standard "Dark World Boss" theme.
    • Wrath of the Lamb had, and may still have, a glitch where secret items don't need to be unlocked to be found.
    • It was possible to enter and exit Challenge Rooms at any time as long as your character could fly. In addition to allowing a player to enter Challenge Rooms without full health, it also allowed players to pick up the item in the room and then leave without fighting any enemies. This glitch was around since the game came out, to the point where it may have become an Ascended Glitch. However, the expansion Wrath of the Lamb made the glitch even more game breaking by including more items that gave flight, as well as advanced Challenge Rooms that always gave a major item. The second update to Wrath of the Lamb removed this bug entirely.
    • Wrath of the Lamb made it though that Curse Rooms only damage your character as he left them (usually, damage is received when entering AND when leaving the room).
    • If you enter a room with 3 charge points or more The Battery in V1.5 (the store retail version with Wrath of the Lamb included) will give you #6 a lot sooner than usual, and reset the counter allowing a further three charges, enabling item use in every room, if you have the patience.
      • Charge #3 seems to happen without the charge icon appearing, and it doesn't affect the count.
    • Also in V1.5, The Habit randomly gives extended Mercy Invulnerability, mostly from enemy shots or contact hits. It doesn't tend to happen with explosive damage.
    • The Luck stat is not calculated correctly in the original game, resulting in Luck Down pills resulting in better drops.
    • Walking through solid walls of spikes is possible due to Hitbox Dissonance.
    • You can steal Deals with the Devil by having only Soul Hearts and an invincibility item.
    • Getting endless money with the IV Bag.
    • Farming boss drops with extra lives / the Portable Slot / the X-Ray Goggles or lots of bombs.
    • Kamikaze can be used without taking damage by pushing against a wall.
    • And the classic of game-breaking circles: Abusing Scapular, the Habit and the D6 or the D20 for infinite rerolls.
    • Libraries and Devil Beggars can have their drops manipulated so that they pull from the regular item pool instead of books (in the case of the Library) or God/Devil room items (in case of the Devil Beggar).
    • More fun item pool abuse: with the D6 as the spacebar item, find Greed. Wait until he spawns minions, then kill him (and only him) and reroll the Steam Sale if that drops; if not, leave the room, come back and kill Greed again in the same manner (since the room doesn't count as having been cleared, he respawns). Repeat until bored, out of re-rolls, or you break the drop system by spawning an Undefined item.
    • In Rebirth, Items that deal damage to you when used are rendered impotent if you have Isaac's Heart—this unfortunately makes Sharp Plug useless, but you can now spam the IV bag without having to engage in door shenanigans.
    • Also in Rebirth, the Broken Remote will still work on infinite-use spacebar items (such as Guppy's Paw) even if they otherwise have no effect.
    • In the Boss Rush mode of Rebirth, if the Carrion Queen's toxic poops are laid over the boss spawn points, then they will be popped on the boss spawning... and can pop a boss if it's moving over that point when the poop respawns.
    • Afterbirth had a particularly nasty one in which the game could suddenly trigger an unlock for Platinum God.
    • Due to the way it works, the Chaos item in Afterbirth, which causes collectibles to be pulled from random item pools, has a tendency to generate multiple instances of Breakfast.
  • Harsher in Hindsight: All of the Guppy-related items were inspired by a real cat who McMillen owned — "owned" because the real Guppy passed away in August of 2014. Where this trope comes in is that quite a few of these items clearly show that the cat in question is dead...
  • Hype Backlash: Considering that The Wrath of the Lamb expansion available for the original version of Issac was absolutely enormous and dirt cheap, many fans thought that Afterbirth, the first expansion for the remake would be comparable to WOTL. It is nowhere near that size, which many fans have felt ripped off by. While many praise new additions like the genuinely interesting (if somewhat buggy) character Lilith, the fantastic and fun Greed Mode, and many of the new items being very fun to toy around with (and boasting even more tasty synergies to fool around with), there are a staggering amount of issuesnote  that have left a good portion of the fanbase extremely upset and disappointed.
  • Internet Backdraft:
    • When the game was barred from release on the Nintendo eShop due to the religious content, all hell broke loose.
      • Thankfully no longer the case as of 2015. Nintendo's former head of indie relations, Dan Adelman, managed to reform Nintendo's outdated and restrictive eShop policies prior to leaving the company to go independent, which finally allowed Binding of Isaac: Rebirth to see an official eShop release on the New 3DS and Wii U in an uncut state.
    • The Afterbirth Alternate Reality Game, or rather what was initially believed to be one. After Edmund and Tyrone (the programmer) teased the community with what seemed like another ARG, it turned out there was none. The missing content from the game was just added after 109 hours, with a patch that on top of that severely (if briefly) nerfed Azazel and a few powerful items. Cue community's complaints, which mostly died down after the real ARG.
  • It Was His Sled: Let's just say that anything in the game that can be considered a spoiler tends to fall into this territory very quickly. The existence of ??? and The Lost, for instance, tend to barely even be treated as spoilers by the community.
  • Memetic Badass: Certain items have this reputation. However, said items are generally useless or arguably downright harmful.
    • Before Rebirth, Abel (a mirrored familiar with the power of basic familiars) was the most common example, but since then, it had to share the spotlight with Aquarius (tracks low-damaging trail of tears on the ground).
    • Bob's Brain (an item that is a bomb that can be shot towards enemies, whether or not you want it to), best item in the game!
    • Nothing stands between Bumbo and his coin. Not even Hush.
    • The Glowing Hour Glass is gaining a reputation as being the solution to literally everything.
  • Memetic Mutation:
    • One of the most popular emoticons on Twitch is BibleThump, which is Isaac crying.
    • "It's not a won run yet!" tends to be used for very powerful runs, which came about due to Northernlion consistently saying it for runs which were very easy.
    • People messing around with the intro narration has resulted in The Isaac of Isaac. One of the Community Remix devs is currently making a mod that replaces all item textures with Isaac, turning this masterpiece into a playable experience.
    • CHUB DISLIKES SMOKE!explanation 
    • Yay, Cancer!explanation 
    • Ultra Greed's Ass explanation 
    • 109. explanation 
    • Are you enjoying the steak? Remember to chew it slowly or else...explanation 
    • Shh, don't let Edmund hear about x, he might nerf it...explanation 
    • Two words: "Dank Depths".explanation 
    • FUCK BLOATexplanation 
  • Moral Event Horizon: Isaac's mom crosses it at the start of the game when she tries to murder her own son.
  • Most Annoying Sound: Isaac's 'hurt' sound when he takes damage has no variation, and if you have to hear it several times in a row, it quickly becomes grating.
  • Most Wonderful Sound:
    • The high-pitched cue when you pick up a dime.
    • The jingle that plays when finding a Secret Room in either version. The Rebirth one is notable enough that it plays when selecting Rebirth on the New 3DS menu.
    • The narrator calling out the name of any pill or card used, especially if it's one with a beneficial effect. The really nice voice doesn't hurt.
    • The angelic choir when you pick up a Soul Heart, or the triumphant note of picking up an Eternal Heart.
    • The combination of "pinball bonus"-like sounds when you use a pill with a positive effect.
    • The sound of an Angel or Devil Room opening up after a boss kill. Unless you have to fight Krampus, that is.
  • Narm: The True Final Boss of Rebirth is undeniably awesome in every way...except for his name. His name is Mega Satan, which, while intended to make him more awesome, leads to this instead.
  • Nausea Fuel: The environments and enemies are all really gross, from the giant turds lining the floors, the enemies that look like giant anuses firing out laser beams, grotesque monsters lined with all manner of horrific markings... ich. The Rebirth remake adds more details, including things like tiny maggots crawling around the floor in large numbers.
    • The Womb's music track in Rebirth, "Viscera", contains... indescribable fleshy sounds that might be a little unnerving to some players.
    • The Scarred Womb in Afterbirth may be the most nauseating environment to look at in the entire game. The name should sum it up quite well.
  • Nightmare Fuel: It has its own page.
  • Rescued from the Scrappy Heap:
    • Samson in Rebirth, following his transition from the original game. While he was originally despised for having low health and having an ability which lasts only one room, the remake greatly increased his health and made his ability not only easier to achieve, but also last the entire floor.
    • The Lost in Afterbirth. Originally a One-Hit-Point Wonder whose only special ability was flying, the expansion greatly buffed him three times. He now starts with the D4, spectral tears, and the Holy Mantle (though the latter item must be unlocked first), which makes the game significantly less frustrating for those playing as him. Another patch made his unlock process significantly easier to accomplish, which no longer makes it a Guide Dang It affair.
  • Scrappy Mechanic:
    • The Sacrifice rooms, where you give up health to get some random chest, are almost entirely useless and feel like a leftover. Rebirth did add a somewhat useful purpose to them, but it's almost pointless since knowledgeable players avoid them like the plague.
      • As of the December 6th patch, Sacrifice rooms have been reworked completely, with the tier of reward changing based on how many times you have hurt yourself. Notably, the rework also makes it significantly easier to fight Mega Satan, making 100% Completion easier. See here for more details.
    • In the original game, the Polaroid trinket is needed to enter the Chest. Unless you have Mom's Purse to double your trinket capacity, this means sacrificing a potentially useful trinket for four levels in order to use it. Rebirth mercifully fixed this by turning it into a passive collectible, though this comes at the cost of Mom dropping a potentially useful item (though, if you get the Boss Rush, that can make up for it). The Eternal Edition of the original made Mom's Purse a guaranteed drop from Mom, making so that while you lose a regular boss item, you get to keep both trinkets.
    • The Headless Horseman and Conquest, for players trying to assemble Meat Boy/Bandage Girl. Both count as Horsemen but only drop their respective Pony item, instead of a meat cube/bandage ball. On the same subject, the addition of Bandage Girl in Rebirth makes getting either achievement twice as hard, because now neither one is guaranteed to drop.
      • And just in case the quest wasn't hard enough, in Rebirth, sometimes your biggest savior can't even help you. The Book of Revelations no longer exists in the Shop's item pool, and using it won't cause a Harbinger to spawn if the floor contains a Double Trouble! boss (or Mr. Fred, as he takes up two rooms). For many a player, their run of resetting for a Basement I BoR was ruined by two Gurdies in the Womb. (Fortunately, summoning Meat Boy and Bandage Girl through the Monster Manual counts towards the achievement, so if you have a way of guaranteeing rerolls, then it's simpler to simply spam that instead.)
    • Rebirth added several new curses. While most are not a problem (and the first floor Labyrinth curse now leaves both Treasure Rooms unlocked), Curse of the Blind is absolutely terrible. The curse has the effect of making you unable to see the pedestal items on that floor, replacing them with a question mark icon. This can screw a run in so many ways it's not even funny. Treasure Room items become a gamble that can have you pick up something terrible like My Reflection, Devil Room items run the risk of saddling you with the Dead Cat on top of costing the health you paid for it, shop inventory costs you 15 coins for something you can never use... the whole floor essentially becomes a roulette wheel you can either try for potential help or ignore for a lost floor of items. The worst of it is when you manage to land the curse on The Chest, where the starting room gives you four free items.
    • Four of the challenges have the Blindfolded mechanic, which completely disables Isaac's ability to fire tears, including Mom's Knife. Not only does this make killing enemies a lot more difficult, all of the associated challenges saddle you with terrible loadouts. Solar System is nothing but orbitals, which have poor range. Cat Got Your Tongue only gives you Guppy's Hairball as a weapon, which is unwieldy at best. Beans! forces you to rely on bombs, which means your run may potentially be ruined if you run out. The Family Man gives you three familiars, but they have a slow rate of fire and you have to beat Isaac with them.
      • Afterbirth features a character with this mechanic: Lilith. It's not quite as bad as the challenges above, however, as she comes with an Incubus familiar that acts as her tears, and gains in power through items just like a normal character would. She also has an item that makes another familiar for each one she currently has that last until she leaves the room.
    • In Rebirth, special items become this. Almost every special item is a Game Breaker, but merely seeing them (no, this does not mean "pick the item up", all it takes is to literally see them) is enough to lower the chance of seeing another special item. Normally this would be fine, but if you see a special item like Soy Milk or Stopwatch, have fun finding a powerful item for the rest of the run!
    • Donation boxes and their preference for jamming. In regular gameplay this isn't so bad, as you'll frequently toss a few coins into the box during each run and build it up naturally in tandem with your normal gameplay progression, and the rewards you get are relatively minor (other than the doubled shop size). However, the donation box at the end of Greed Mode is required to unlock a lot of character buffs and items, and for some players they'll frequently go through twenty minutes of Greed Mode, trying to develop enough of a hoard to put into the box... and then it jams after three or four coins. Someone did the math, and assuming optimal conditions, it would still take at least 90 Greed Mode runs to actually fill the machine. The same patch that unlocked Keeper made it much easier to fill the box, as it now takes a lot of coins to jam the machine.
    • Afterbirth introduces damage scaling. Pretty much, the two main endgame bosses introduced are supposed to encourage more defensive builds, having high health pools and focusing a lot more on learning their different attacks. However, instead of just giving them high health, they also have a mechanic where their defense increases based on how much damage you're outputting. This means that it doesn't matter if you have an extremely low attack stat or if you have powerful game-breaking combos, the bosses will take roughly the same amount of time to defeat either way. In fact, getting too strong might be a negative against one of the bosses, as if they scale their defense high enough in tandem with their healing ability, they'll become impossible to kill.
    • Half-size rooms. You wouldn't think they'd be that big of a problem, but surprisingly several of them become Unwinnable by Design through no fault of your own. One example is Krampus or Forsaken, who have rotating Brimstone attacks. These attacks are unavoidable if they're hugging the wall, and in a half-size room that's virtually always true. After enough player outrage, there was a patch released that reduced the odds of half-sized rooms appearing, but no patch as of yet to prevent unavoidable damage.
    • The new pill effects from Afterbirth received a less than positive reception, due to them mostly running the gamut from "not very useful" to "actively harmful". It also doesn't help that effects that turn bad pills into good ones have no effect on them, even the ones that are unconditionally detrimental, and that a number of them have to be unlocked by doing challenges. The worst of the vitriol by far is directed towards the Retro Vision pill, which does nothing but periodically pixellate the screen for a short time. Not only do many players find it pointless and annoying, but some players have reported actual discomfort of the eyes resulting from the effect, while others report that the effect causes severe lag. The hatred for the effect is bad enough that many players are clamoring for it to be removed from the game completely.
    • Angel Rooms in Rebirth. While they were guaranteed to contain a free item in the original, Rebirth Angel Rooms more often than not contain pickups, which generally aren't nearly as helpful. Additionally, to get these to appear, you have to pass up a Deal with the Devil, which more often than not grant items whose power more than justify the health cost and are usually much better than the standard Angel Room fare. Players usually only deal with Angel Rooms in order to take on the True Final Boss, which requires you to find two of them in the same run — which, due to the Random Number God, doesn't always happen even with optimal circumstances (or worse, forces you to skip items like Brimstone).
  • Scrappy Weapon: A few.
    • My Reflection is a particularly infamous one, as it just makes your tears boomerang around wildly, cutting your range and making it hard to aim. Some combinations using it will screw you even harder, such as combining it with IPECAC or Bob's Rotten Head, causing your explosive projectiles to boomerang right back at you. Even worse is that the Suicide King challenge in Rebirth sticks you with the My Reflection + IPECAC combo for the entire run. It works surprisingly well with Azazel, however, as it's one of the few items that increases his otherwise short range.
    • Bob's Brain and BBF in Rebirth. There's nothing worse than being in the middle of combat and having them respawn and explode on top of an adjacent enemy, catching you in the blast. Sometimes, BBF can even damage you as soon as you enter a room! Bob's Brain, at least, was toned down a bit in Afterbirth, as it now can't be fired for a few seconds after it spawns or after you enter a room, preventing surprise explosions.
    • The Cursed Eye. While the quadruple charge shot is nice, if you are hit while charging the shot, you will be teleported to a random room. This makes fighting bosses very problematic, as even one mistake can warp you away and ruin all of your progress. Fortunately, this drawback is easy to work around, and can even be beneficial in some circumstances. Most notably, allowing you to take a free item from the Boss Rush room.
    • The Stopwatch, which is frowned upon for either being too powerful or too weak of an item, depending on what version of the game you're playing. In Rebirth, it is a huge Game Breaker which slows down enemies and projectiles for the entire game. In Afterbirth, however, the slowdown effect not only lasts one room, but only activates if you take damage.
    • Rebirth also gives us Soy Milk, which, at the cost of slashing 80% of your damage and tear size, massively boosts the firing rate of your tears, to the point that a starting Isaac with Soy Milk has enough of a fire rate to shoot 30 tears per second. Unfortunately, the game has a hardcoded limit of 15 tears per second, meaning that while it's technically a bit more DPS than your default tears, that's only if you make every shot count. Given the game's enemies and their erratic movement patterns, making all your tiny tears hit their mark so the damage output is at least decent is a pain in the ass. The DPS is so poor, all bosses become Marathon Bosses, and even flies take a lot more shots before they're down. And to add insult to injury, it's a special item, so once you see it, your chances of a really good item in your current run fall dramatically! Only once you gain a lot of DMG ups or synergize Soy Milk with other certain items does it become a Game Breaker, due to its high firing rate carrying over. Fortunately, in Afterbirth, Soy Milk is no longer a special item, meaning that it no longer interferes with your ability to get really good items just by showing up.
    • Of all items, Dr. Fetus is this in Rebirth. In the original, it was seen as a borderline Game Breaker due to its tremendous damage output, but also carried a high chance of damaging yourself. In Rebirth, Dr. Fetus bombs had the self-damage reduced, but also suffered a massive damage drop, meaning that it now fails to consistently One-Hit Kill many normal enemies and kills bosses very slowly. It did also receive an increased fire rate, which theoretically makes Dr. Fetus an overall damage upgrade, but in practice tended to cause bombs to knock each other around — often into the player's face. It doesn't help that fellow explosive attack Ipecac has the same self-damage, but deals much more damage to enemies. However, if the PAX Prime footage is any indication, Afterbirth will likely restore Dr. Fetus's damage to original-game levels.
    • Afterbirth also brings us the Glass Cannon. On release, it reduced the user to half a red heart, but gave you an on-command massive tear with scaling (but always high) damage. However, as of the November 4th 2015 update, it now reduces you to half a heart — including soul hearts and black hearts — turning the user into — appropriately enough, given the name of the item — a Glass Cannon. To say that people are not amused is a massive understatement.
    • The Butter Bean, in all versions of the game. It's a spacebar item that only has the effect of producing a small fart that can knock back some enemies. At least it recharges spontaneously in Rebirth, and in Afterbirth it can deflect bullets.
  • Self-Fanservice: On occasion, most often happening to Eve. It might have something to do with her starting item...
  • That One Achievement:
    • The No Damage Run achievements. At least they're mercifully divided into groups, so you don't have to go through all eight in one run.
      • The king is the Dark Boy (Depths) No Damage Run. That level set has just the right combination of pits, Demonic Spiders, Goddamned Bats, indestructible moving spike blocks, and cheap-as-hell bosses (plus Mom) to make it an absolute nightmare to get through, no matter how absurdly overpowered your character is. Even the Womb is easier because it does not have pits. Rebirth made the Womb somewhat more difficult by adding pits.
      • Rebirth ups the ante on that one with Dead Boy, achieved by completing one of the game's Brutal Bonus Levels, The Chest or the Dark Room, without taking damage. Here's hoping you packed a Holy Mantle... though it is slightly easier on The Chest, as four free (as long as you have keys) items are available from the starting room, and there's a chance to find more after completing every vicious room.
    • Rebirth has The Lost. Unlocking it is a massive Guide Dang It and a Luck-Based Mission for the first part, though you can mercifully use seeds. Then, once actually unlocked, you have to do no damage runs of the entire game through both Brutal Bonus Levels (Mega Satan is optional) and the boss rush, and then do it all again on Hard mode to unlock the Godhead.
    • Assembling Super Meat Boy and Bandage Girl in Rebirth. In vanilla Isaac and WOTL, assembling Super Meat Boy wasn't too difficult to do as long as you got the Book of Revelations early enough. And you didn't have to assemble it to get the achievement, just kill all 4 of the Harbingers in one run. Unfortunately, the Book of Revelations no longer guarantees a Harbinger boss fight, instead giving a higher chance to run into them. The real kicker is that they now drop a Cube of Meat or a Ball of Bandages, so you have to hope the first one drops the item you want. Running into the Headless Horseman or Conquest will also ruin your chances of getting the achievements. Counter-intuitively, these achievements are actually easier if you go out of your way to avoid unlocking Conquest (which requires getting ten Angel Room items). Once Conquest is unlocked, it becomes downright impossible to manage a fair playthrough where you get the whole set. It's considered a lot less luck-based just to set up a way to infinitely recharge the Monster Manual to get a level 4 Meat Boy/Bandage Girl. It says something that these achievements have a lower completion rate than almost every other achievement in the game, second only to the shop unlocks and all of the Lost's achievements. Mercifully, Afterbirth made this incredibly easy to earn with the addition of Greed mode and Lilith. Lilith's active item, Box of Friends, duplicates any familiars she has for the room it's used in. With Cube of Meat/Ball of Bandages, the effect is an immediate upgrade with each use. Greed mode's wave mechanic allows you to use the box at least three times in a row, since the charges accumulate with each wave. In tandem, this means you only need to find one of either item to get the associated achievements. Boss Rush or a 48 Hour Energy pill in the main game will also work.
    • Collecting all of the items for Platinum God and Real Platinum God in Rebirth is far more annoying than in the original. This is mostly due to two reasons: the Secret Rooms and Steven. Secret Rooms have a much greater variety now, most of which do not contain items, which combined with a larger number of exclusive items means it is that much more difficult to get everything from that pool. Most resort to Loophole Abuse with the D6, Judgement cards, and mushroom drops. Steven was originally a nightmare to find in Rebirth due to only being a rare boss drop, but Afterbirth has since fixed this by putting Steven back into the golden chest pool.
  • That One Attack:
    • Mom's hand during the Mom boss battle, not to be confused with the Mom's hand monster in Rebirth. It comes out to swat you if you hang around the doors too much, and is near-instantaneous. It's avoidable, but you probably won't manage to do it on purpose. Playing as The Lost? Game over.
    • The Bloat's brimstone attack, which once again has no tell and hits almost instantaneously. And he'll use it without fail if you get in range.
    • The Adversary's Brimstone attack. It's telegraphed by a unique roar, but that's of little comfort when the beam actively curves to hit you. While it is possible to dodge by getting close and circling the boss, this attack becomes a terror when two Adversaries are in a single room and the one in the other corner unleashes the beam.
    • Mega Fatty, an otherwise easy to dodge if spongy boss, has one really annoying attack. He can, with almost no warning, leap from his current position to where you're standing in less than a second, which is practically undodgeable if you're standing still.
  • That One Boss:
    • Gurdy, a Damage-Sponge Boss early on, can't move but takes up half the room. She can fire five bullets in a spread pattern and summons sacs that fire more bullets, as well as flies. Compared to the other bosses, she's a real pain. It's easy enough if you get her pattern down, but the fight takes a long time. You also better hope you've upgraded your damage or tears, because the bullet sacs regenerate a lot faster than spider sacs do. A lot easier if you learn to exploit the space behind her where flies spawn, even easier if she spawns an explosive Boil, which tends to hurt her more than you.
    • The Widow from WOTL, a first-floor boss that jumps around like crazy, spits demonic spiders (the tiny kind), AND spawns sacs that in turn spawn more demonic spiders. Then there's a variation of this which spawns even MORE spiders, double spiders, and hopper spiders. She was thankfully toned down after release, but she's still a lot tougher than most bosses on that floor.
    • The Mask of Infamy, a giant copy of the mask-heart enemies. Don't let that description fool you. Its AI is a lot better than the mooks it takes from, and both the mask and heart need to be killed. The mask can only be hit from behind, and has near-perfect turning reflexes. If you don't have a piercing attack, expect to spend a long time fighting.
    • Super Wrath. He fires the homing troll bombs that pass through walls, and is tougher to kill. If you can't fly, it sucks to be you. Rebirth mercifully toned this down by making his troll bombs solid, and boss fights with him usually have indestrcto-blocks to stop the bombs.
    • The Bloat. A ruthless version of Peep that invariably fires Brimstone the same second you enter the room, and also if you so much as graze the area directly to the sides or in front of him. Unless you've got very high speed, this will hit you. The only safe place you can attack from is behind him, and his eyes always seem to be behind him. Oh, and the eyes detach at start, not after taking enough damage like Peep does. A champion version will also send out a spray of Ipecac bombs towards you whenever he jumps, and can spawn Chargers. It is also possible to fight him in both Necropolis and Utero on the same run. If you get to The Chest (or the Dark Room in Rebirth), always have more than one heart in case he turns up unannounced.
    • Gurdy Jr. Not so hard right? Then she charges at you with ridiculous accuracy. And if she misses, she might just do a little homing slide into you. The variations and double boss versions only make her that much harder to defeat. Plus, like "her mother" Gurdy, Gurdy Jr. is one tanky boss. Rebirth's Double Trouble mechanic can actually saddle you with four of these guys at once.
    • Several of the Harbingers and Horsemen qualify. They all drop Cube/Bandage familiars (or Pony items) without fail, which can be annoying if you need a health up.
      • The Headless Horseman is a Dual Boss. The body shoots bombs constantly, while the head shoots bullets with almost no warning and charges frequently. The charges will cover top, middle, and bottom, and not always in the same order. The head also appears as a Degraded Boss, sometimes more than one at a time.
      • Conquest, the new horseman in Wrath of the Lamb, has a charge which covers almost the entire screen, which can be impossible to dodge if you're too slow or get trapped too far from the safe area. There's little warning for his fast moving homing shots, and the beams he releases from the sky are impossible to dodge by your own ability (unless you have flight), you just have to hope they don't hit you. His AI sometimes has a small pathfinding bug where he slowly drifts into a corner and into the wall where normal tears can't hit, while he can simply teleport of screen to do more damage to you. Combine that with his whole heart damage for everything he does and Conquest can end your game. Conquest's gameplan is mostly teleporting so rush attacks (Game Kid, Unicorn, The Chariot) are much less useful than with most bosses. To make it worse, while Conquest can usually only replace Death, due to a glitch, he can also randomly replace War, who is fought two floors earlier.
      • Death, the final Horseman, is able to summon Scythes that home in on you. It's limited homing, but they are huge and hard to dodge. After you've damaged him enough, his mount detaches with its own health and charges endlessly, even after you've killed him. On top of that, he spawns Knights.
      • Pestilence is mostly a pain because of room design more than anything else. Fortunately, his ipecac blasts will clear the rocks out eventually. Unfortunately, he is spawning grubs all over, and sometimes rapid fires his ipecac blasts which also cover the floor in toxic do-not-touch spots. Once you get to his second stage it is easy... good luck getting to his second stage one more than a heart or two. He's even worse in Rebirth, as his ipecac blasts are faster.
      • And if you are unlucky enough to get a Pestilence and Headless Horseman combo in the Chest, here is hoping you got a lot of good upgrades on the way.
    • Ultra Pride is a Dual Boss. The main boss (Edmund) always does one full heart of damage without the Wafer and has an attack where he spontaneously creates a giant poison stream in front of him with long range. Then there's the familiar (Florian), who behaves like the Babies, meaning that he can teleport. In addition, he fires fast moving, long-range homing tears; the exact same type fired by Isaac and ???. Also unfortunate is that, if you're going for Platinum God, you must defeat Ultra Pride at least once.
    • The Blighted Ovum. Similar to Gemini, this one has the added "benefit" of being the same speed as the player sans-powerups and leaving behind lethal blood trails that deal A FULL HEART OF HEALTH IN DAMAGE, along with a "little brother" that uses Brimstone. And the blood trails stick around for just enough time that you will step on one after completing a circle around the room. If the Ovum isn't dead or close by then, and you lack flight, you are very screwed.
    • The Haunt. At first, he's completely invincible and relies on his three smaller ghosts to assist him, but once they're killed he starts his attacks. The Haunt is actually very fast once he starts attacking, making it difficult to lead your shots to him. Not only does he have an untelegraphed bullet spread attack, but he can also fire a Brimstone laser vertically across the screen with barely a second of warning. And if you think you can just run off to the side of the Haunt to dodge this, think again. Doing this causes him to charge you for a full heart of damage. And the best part? He's a Cellar boss, meaning he can potentially be the first boss encountered in a run. Some fans have come to the conclusion that he's even harder than the Widow, the previous infamous Cellar boss.
    • The Adversary, which is the advanced version of the Dark One. The one and only thing that stands out about the Adversary is that he fires a Brimstone laser that homes in on you. This becomes incredibly problematic if there happens to be two of them in one room, as it gives you almost no room to dodge one Adversary's laser while avoiding the other Adversary's own attacks. If the Adversary manages to wander into one of the corners, you're toast.
    • The Cage, which is pretty much an oversized Vis. For starters, he has the highest health of any boss in the game (with the exceptions of the final bosses), higher than that of Gurdy and even Mom. As for his choices of combat, he possess a rolling attack that is similar to Gurdy Jr's charge but without the ability to slow the boss with knockback. The real show-stopper, however, is his jump attack that sends out waves of stone that curve completely randomly and are impossible to predict. And yes, there's the chance of seeing two of them in one room in the final levels. Afterbirth introduces a pink champion version of two Cages, which can result in a Double Trouble room having four Cages at once.
    • Carrion Queen can be difficult not because the boss herself is strong, but because she leaves behind damaging red poop that quickly regenerates if destroyed. On top of that, much like Scolex, only her end segment is vulnerable to attack (though getting her to swallow bombs works, too). If you don't damage her fast enough to trigger her second phase, the arena will be a minefield. The champion version is actually better, because she instead poops out tiny heart enemies which are easy to kill. She's both a blessing and a curse during the boss rush, in which her poop can blend into the all the bloodstains and become almost impossible to see, but will also cause major damage to the other bosses, potentially killing them in a few seconds.
    • If your speed is abysmal enough (like starting with Magdeline), then bosses that chase you at high speed like War, The Fallen, and Lust can be an absolute nightmare.
    • The original game's Eternal Edition makes even the easiest bosses much harder than any normal boss fought in Rebirth or pre-Eternal, especially since it introduces the brand new concept of Regenerating Health. For starters, the Eternal version of Mom's Heart/It Lives (which is normally an Anticlimax Boss) will constantly chase the player and slowly regenerate health, while retaining the ability to spawn enemies and the occasional Degraded Boss.
    • The Stain from Afterbirth, the upgraded form of Polycephalus. Like the original, it spends most of its time underground, popping up only to attack. While this is predictable most of the time, if you don't get it to pop up before it disappears, then you have no idea where on the field it will show up. This means it can easily get in your face to use its Combat Tentacles attack, which is very fast and has virtually no tell aside from the Stain appearing in front of you. That is, if it doesn't go for just popping up directly underneath you for unavoidable contact damage. If that isn't bad enough, if it pops up as a single face, it uses a Bullet Hell attack with a volume comparable to Mom's Heart. Finally, Greed Mode can pit you against two Stains at once, or, if you're really unlucky, three. God help you if they all use their Bullet Hell attack at the same time.
    • The red champion version of Mega Fatty. Not only does he still have That One Attack mentioned above, said attack now shoots bullets in all directions when he lands (which will generally be right next to you). On top of that, he has a second dangerous attack: instead of the regular version's easily-dodgeable Waterfall Puke, he follows up his "sucking in everything in the room" attack with a Mom's Heart-esque Bullet Hell attack. And, of course, he still has a ridiculously large health pool. To top it off, Greed Mode can make you fight Mega Fatty on the first floor. Annoying enough if it's the regular version, but if it's a champion, you might as well restart.
  • That One Level:
    • The Cellar can be a much harder starting point than The Basement, usually involving harder enemies and rooms with a borderline fetish for spider enemies. In addition these levels can frequently stick you facing either The Widow or The Haunt as your first boss battle of the run.
    • Necropolis. Not only is it home to quite a few Demonic Spiders (such as Hangars and Masks + Hearts) and numerous spike traps, but it also holds some very annoying bosses like The Bloat and The Mask of Infamy. Fortunately, the latter only applies for Necropolis 1, as Necropolis 2 always has Mom as the floor's boss. There's still the risk of them spawning in Boss Challenge rooms, though.
    • The Dark Room, when compared to fellow Brutal Bonus Level The Chest. While the four initial chests in the latter all contain items, the ones in the former are red chests with the usual fare, meaning that there is no guarantee of getting anything that helps you survive the level. Additionally, the Dark Room tends to contain more dangerous enemies than The Chest, including the likes of multiple Fallens or even Mask of Infamy.
  • That One Sidequest: Most of the challenges, especially the ones included in Afterbirth, qualify as this. Notable offenders include:
    • The Suicide King challenge in Rebirth. Have fun playing the entire game with exploding tears that boomerang right back in your face!
    • The Family Man challenge is probably the the hardest of the base game. You're blindfolded, and your only means of damage are through three familiars. Thankfully, one of them is Rotten Baby, which scales with your damage, but other than that, you're gonna have a very hard time trying to damage enemies even a little bit. It's borderline impossible to complete the challenge without resorting to resetting until you can get a Cube of Meat or Ball of Bandages on the first floor.
    • The Speed! challenge in Afterbirth. Enemy movement and bullet speed are dialed up significantly while you start as basic Isaac. There's Treasure Rooms, but that's little comfort when bosses like Gurdy Jr. can move twice as fast and become practically unavoidable. Oh, and if you don't finish all the way to It Lives in under 16 minutes, you get half a heart of damage every few seconds which can kill you! It goes to the point it's almost impossible to even beat the first floor if you get a hard boss unless you get a good start. It's basically saying "reload until you get Brimstone or something else that kill instantly, otherwise you lose." A patch eventually increased Isaac's movement speed as well, making the challenge slightly more manageable in that you'll at least be able to outrun most enemies that chase you.
    • The Brains! challenge, again in Afterbirth. You're not only blindfolded, but your only offensive weapons are three Bob's Brains, which is a Scrappy Weapon infamous for its tendency to blow up right in your face. What makes this worse is that you're playing as ???/Blue Baby, making it more difficult to recover health.
    • The Guardian challenge, once again in Afterbirth. You must protect Isaac's Heart which isn't following you, but rather the Punching Bag that wanders around the room. Oh, and the Punching Bag is the one that takes damage, not the heart. You have no real control over whether or not you take damage, as all enemies attack the Punching Bag rather than you. Hazards like red poop and spikes turn the challenge into a Luck-Based Mission due to the fact that, if the Punching Bag touches a hazard just once, you lose a lot of hearts instantly!
    • Most challenges where you're blindfolded and thus unable to fire tears falls into this category, such as "Cat Got Your Tongue" (rely only on flies and Guppy's Hairball for damage) and Solar System (orbitals only).
  • Tier-Induced Scrappy:
    • Samson in the original game. To put this into account, he's more despised than the game's resident Joke Character\Lethal Joke Character.
    • Eve, too, to a lesser extent. She starts the game with below average health and damage, and her initial abilities are all essentially Cast from Hit Points. Do the math. It's so bad that, before the DLC, the Lethal Joke Character actually had a higher completion rate, despite being more joke than lethal.
    • Rebirth gives both of these characters buffs. Samson now starts with three hearts and his damage stacks don't reset until he leaves the floor. Eve's Whore of Babylon will trigger at a full heart instead of half a heart (it still triggers at half a heart for everyone else). Cain, however, was hit hard with the nerfbat, as his Lucky Foot no longer recycles bad pills. Afterbirth eventually buffed Cain by starting him out with the Paperclip, provided it is unlocked.
    • Azazel is often frowned upon for being largely unbalanced compared to the other characters. To explain, he starts with three black hearts (but can acquire regular health through powerups), flight, and a short-range Brimstone attack. The range issue is at best minor, and Azazel can clear rooms like nobody's business. With a little skill, Azazel can easily make it all the way to Mom in time for the Boss Rush without any significant powerups. With powerups, he's a murder machine. He eventually got nerfed in Afterbirth by having his fire rate lowered, but this can easily be undone with a couple Tears Up items.
    • How about The Lost? He can fly, but he's a One-Hit-Point Wonder and doesn't even start with any items besides one measly coin. The fact that one of his item unlocks requires you to beat every final boss (save for Mega Satan) on hard certainly does not help matters. Fortunately, as Author's Saving Throw mentions above, he eventually got the buff he deserved.
    • Lazarus has negative luck and short range but starts with a pill and the ability to resurrect with 1 heart; problem is, the pill can randomly screw you and the resurrection isn't something you should rely on the first place. So, when compared to the other characters, Lazarus is generally considered to be the most boring.
    • By getting 999 coins in the Greed mode donation machine, you unlock The Keeper (which is basically a playable shopkeeper). Instead of hearts, he has two coin slots; any kind of damage takes 1 coin, but taking another coin on the floor heals it back. Hearts turn into flies, and his maximum health can't be increased but CAN be decreased if you get a item that takes one red heart container. He can't even take 2-hearts devil deals without dying, he ONLY takes red heart damage so any damage you take lowers the chance of a devil/angel room, a lot of items are useless on him, and it only takes an unlucky life down pill and the next hit is a game over. If you find a Swallowed Penny or a Piggy Bank, you're essentially immortal as long as you get money before the second hit, but then the game stops being super hard and becomes super boring.
      • How bad is Keeper? He's frequently unfavourably compared to The Lost, the previous main title holder of Tier-Induced Scrappy. As difficult as The Lost is, he still starts with flight, spectral tears, the D4, takes Devil Deals for free, and unlocks some of the best items in the game. Keeper starts with a single bomb, cannot improve his HP (thus denying him any powerful Devil Deals), is never more than two hits away from death, and unlocks nothing interesting. In short, Keeper has a mountain of setbacks, but no advantage that makes up for the shocking difficulty.
  • The Woobie:

http://tvtropes.org/pmwiki/pmwiki.php/YMMV/TheBindingOfIsaac