Formats: Back in the day, you could nominally play just about everything (a la Vintage), meaning that those that had been playing more than a few years or had a lot of disposable income enjoyed lots of advantages and there was little way around certain bad old cards unless more powerful ones were put out. The introduction of Standard format restricting play to only more recent sets stabilizes the game's power level and reduces the load on a comparative newbie (who can simply refuse to play a Vintage/Legacy/etc deck).
At various times, the popularity and longevity of the game has supposedly been in danger due to poor decisions from the designers, generally manifesting in decisions made in whatever the newest set. This has been going at least since the (famously powerful) Urza Block was followed by the much more modest Mercadian Masques set in 1999. Showing that with time any problems are only a new block away from being fixed, for new ones to emerge and the cycle to to continue.
Wizards dropped Kiora's last name after it was brought to their attention that it resembled a Maori word that touched on a central religious concept.
Doug Beyer: If we learn that any of our worlds, terms, or characters disrespectfully tread on the sincere beliefs of our fellow humans in contemporary, living cultures, we feel its important to take steps to correct that as best we can.
The 4-of rule. The original rules in Alpha didn't restrict players to just 4 copies of a card, and many games would end on the first turn.
Dominaria introduced a variant of hexproof that only applies to specific colors (rather than every targeted effect) as a substitute for the highly-complicated "protection from" ability.
Awesome Art: Hell yes! Magic The Gatherings card art is consistently detailed, vivid, and gorgeous, painting epic, vast worlds that are one of the game's main draws. Even simple cards like basic land cards may get eye-catching art that you wish you could expand and put it on your wall.
Awesome Ego: Nicol Bolas is one of the most evil characters in the setting, but there's no denying his arrogance makes his dialogue a lot of fun.
Jace Beleren. Some people are fine with his multiple appearances in both card form and plot form, others remember the days where Jace the Mind Sculptor dominated every format and hate every incarnation of Jace since. It doesn't help that Jace has been a main character in several major storylines, causing many fans to feel like he has overstayed his welcome.
Nicol Bolas. Some consider him a valid Big Bad and an interesting take on "Dominaria's most ancient evil". Others consider him a Villain Sue who is being shoehorned into every storyline and isn't as interesting as other villains, especially Yawgmoth or the Praetors.
Nahiri. One side argues that, after being forced to use her plane, Zendikar, to seal away the Eldrazi, she did not deserve to be dismissively ignored and stuffed in the Helvault by Sorin, which she believes allowed Zendikar to be destroyed by the Eldrazi. The other side argues that this doesn't justify luring Emrakul to Innistrad, resulting in the deaths, insanity, and mutation of thousands of people.
Broken Base: Examples include "non-interactive" mechanics (cards that limit how other players can react to them). The "Hexproof" keyword ("this card can't be targeted by your opponents") in particular draws a lot of contention from both sides, as satirized in this comic strip.
Cliché Storm: The Innistrad block (purposefully) plays every Gothic Horror trope to the hilt. Restless geists, zombie apocalypse, demon cults, vampire lineages, rampaging werewolves, cackling mad scientists, humankind besieged by unholy darkness...
The Scheme cards from Archenemy are purposefully over-the-top. For example, Behold the Power of Destruction's flavor text:
"I'd call that a successful first test. Golem! Rearm the DoomCitadel!"
Common Knowledge: It's widely known that Crovax from the Weatherlight saga is of the Windgrace family, information that even appears on wikis and other popular storyline sites... but nobody who's looked has been able to find any source for this, only a line about Crovax admiring the planeswalker Lord Windgrace (who is also from Urborg, but otherwise unrelated, being Cat Folk).
Complete Monster: Of all the threats the Multiverse has faced, these are the worst:
Yawgmoth, the first Big Bad, was born a normal Thran in Dominaria during the reign of the technologically advanced Thran empire, about 5,000 years before the birth of the inventor Urza. He was banished for his unorthodox beliefs regarding diseases and healing, but returned to the capital city of Halcyon to treat Glacian, the renowned engineer and inventor, who was suffering from an unknown illness after being attacked by an exiled leper named Gix. Though Yawgmoth was by trade & profession a medic, his ways went towards an unnatural fascination with the mechanics of the body. This fascination led to experiments with plagues and poisons, several of which caused widespread death among the various races that he had visited. Yawgmoth was also slowly draining Glacian's soul to fuel his own power. Yawgmoth later learned about planes from the wizard Dyfed, until he subdued her and gave her to his followers for dissection. Ruling his own realm, Yawgmoth plotted further conquest, corrupting and killing other heroes and innocents. When he invaded Dominaria, he killed millions of innocents before he was destroyed.
Nicol Bolas, one of the next Big Bads, is an elder dragon Planeswalker over 25,000 years old who loses his near-limitless power when the nature of the Planeswalker Spark is changed, and dedicates himself to getting it back at any cost. A master of red, blue, and black magic, Bolas excels at breaking minds and bending people into submission. He collides the five worlds of Alara into each other in an attempt to absorb the energy released. On Zendikar, he manipulates three Planeswalkers into setting free the Eldrazi Titans. As New Phyrexia grows on Mirrodin, he sends an envoy to reach out to the blossoming parasitic plane in the form of Tezzeret, a Planeswalker whose mind Bolas has broken and enslaved. He travels the Blind Eternities, endangering one world after another with each scheme in his quest to regain omnipotence. In addition to all this, in Emperor's Fist, he outright boasts about causing genocide for shits and giggles.
Ob Nixilis is a human Planeswalker who, in his mortal life, was a cruel, despotic tyrant, bent on conquering his home plane. Eventually defeated by his enemies, Nixilis sacrificed his last loyal soldiers to summon demons who fulfilled his heart's greatest desire: the death of all life on his plane. Despondent over having no one left to rule, his Spark ignited and he began wandering the Multiverse and scouring the life from every plane he came across. After turning into a demon from using the Chain Veil, Nixilis fled to Zendikar to use its mana to remove the curse, but lost his Spark instead. Nixilis was willing to destroy Zendikar itself to regain his power and tried to devour Zendikar's soul, and, failing that, finally regained his Spark by absorbing the hedron network keeping the Eldrazi titan Ulamog imprisoned. As a final act of spite toward the world he hated, he awakened the titan Kozilek to ensure Zendikar's doom. Driven by his lust for power and conquest, Ob Nixilis was willing to raze the Multiverse to regain the humanity he never had.
Crack Is Cheaper: Magic: the Gathering is infamous for this trope. Many very strong cards are also very, very rare, and can be worth between 10-40 dollars for an average 'Standard-tournament worthy' Mythic Rare, or even more for the exceptional ones. Tournament decks typically consist of many very valuable cards, and consequently it can cost many hundreds of dollars to make a Standard tournament deck, and Standard is one of the cheaper formats, though not the cheapest. The most expensive format, by far, is Vintage, which is a format that allows all cards from all genres, and doesn't ban cards that are too strong. One single card in Vintage, such as Force of Will or Underground Sea, can cost hundreds of dollars, and the most expensive Magic card of all time, Black Lotus, costs several thousand dollars, though some cards (such as Black Lotus) are restricted to one copy in Vintage (to keep the format from getting too ridiculous). The expense of Vintage cards can make a powerful Vintage deck cost many thousands of dollars. As of January 2015, only 41 cards have been restricted in Vintage (the restricted list can be found here).
Creepy Awesome: Old Phyrexia started the trend and now New Phyrexia is running on this. Not only they turned Mirrodin into a hive-minded world that runs on Uncanny Valley, they have managed to compleat angels. And we love them for it.
"It's so cute when it's sleeping, isn't it? Actually, it's still as abhorrent as ever, but at least it's not trying to kill us."
Darkness-Induced Audience Apathy: While not universal, this can occasionally happen in the backstory due to a fumbling of the Morality Kitchen Sink of the factions. The idea behind each of the colours (or colour combinations) is that they all have equal capacity for good and evil. Unfortunately, some writers forget this and put too much focus on showing that the "Good" colours (like White) have an evil side, while forgetting to then make the "Bad" colours (like Black) more sympathetic to compensate creating a setting where Light Is Not Good, and Dark Is STILL Evil.
Jace is not really given the moral high-ground in Agents of Artifice. It's more of a portrayal of a character who starts out neutral, slides toward evil due to negative influences, and finally manages to pull himself at least somewhat toward the side of good. He's pretty aware of just how bad the shit he's done is, though.
Venser, just Venser. In his first appearence on the Time Spiral Cycle, he is obnoxious, quite vitriolic, and more interested in getting to Jhoira's pants than the larger stakes. When he reappears in the Scars of Mirrodin shenigans, he is triumphantly depicted as a standard hero and a personal friend of Karn, a person whom at best he was ambivalent to and at worst outrightly aggressive towards. To make matters more hilarious, in the actual novel for the set, Quest For Karn (incidently the last proper novel for Magic as a whole), he is a belligerent drug-addict who spends most of his time bickering with his companions (albeit not without reason). When he gives up his life to save Karn, the audience is expected to see it as a Heroic Sacrifice, but most are left with a sigh of relief.
Sarkhan Vol on the Khans Of Tarkir shenigans. The narrative paints his endeavours to go back in time and save the dragons as a good thing... except that the end result is considered by many to be worse, since the clans have been subjugated by the dragons and degraded into shadows of their former selves. Though Creative maintains that this was the purpose, the narrative in the player guides and uncharted realms (as well as the land art) clearly suggest that this new Tarkir is meant to be better. Only one dissenting voice is heard, Yasova's, but she is shown as being in the wrong.
This may be somewhat deliberate, though. Significant chunks have been seen from the POV of Sarkhan or the new dragon-ruled clans and only Sarkhan is aware of both timelines, and his views are obviously colored by his obsession with dragons. During the "Khanfall," Shu Yun had maintained Ugin's desire for balance between the clans and dragons, and we've yet to really see Ugin's opinion on what has become of Tarkir, though obviously he prefers this version because his only view into the other timeline is through Sarkhan and this timeline has the chance to be "fixed." Either way, one really has to wonder what the Narset of the old timeline would think of the new timeline.
Teferi, at least in the Dominaria set. While not a bad guy, his card from that set declares him the "Hero of Dominaria", which isn't really deserved. During the Phyrexian Invasion, one of the greatest threats to Dominaria's existence, Teferi decided not to fight the Phyrexians, and instead phased his homeland of Zhalfir (as well as Shiv) out of existence before leaving, despite Urza pointing out that doing so would mean Dominaria losing powerful allies in their war against the Phyrexians. In essence, in one of Dominaria's most desperate times of need, rather than aid Dominaria, Teferi decided only to save the parts he cared about most before leaving the plane to its fate.
Double Standard: Counterspells are a very divisive aspect of Magic because they can take down large spells at a comparatively low cost, but direct damage and creature kill have the same practical effect and get much less hate. To be fair, more cards exist to defend against the latter, while the former can only be defended against by other counterspells or very specific and rare cards which are explicitly immune to counterspells, but the hate primarily comes from the psychological perception that they prevent a card from being played at all more than the actual gameplay.
Yawgmoth, and Phyrexians in general. When they first appeared, they were barely a footnote in the flavor of the Antiquities expansion; eventually, they morphed into the main villain in Magic's Rogues Gallery.
Alesha may qualify, being Magic's first transgender character and getting an overwhelmingly positive response from the fanbase at her character (Doug Beyer himself thanked his readers on his Tumblr), but the real star has to be Jagun Wingmate, the nameless orc that gave Alesha her war name. Mark even acknowledged his popularity on his blog as well.
Halana and Alena, a pair of characters who don't even appear on cards, swept the lore-loving Magic community by storm when they appeared in the story for the Shadows Over Innistrad block, because they're a pair of lovers who are resourceful, clever, and strong enough to survive the entire block, which is no small feat, considering the amount of Nightmare Fuel present. Avacyn didn't even survive it! People have been asking for a card featuring them since.
Ajani Goldmane has gained quite a following since the publication of a story from his point of view in the Kaladesh block, Release. People are arguing that, despite the fact that he's going to most likely be the Token Non-Human member of the Gatewatch (Nissa notwithstanding), this story made him seem more human than any of the current Gatewach members. Helping this is the fact that Ajani has a fair bit of badass cred from essentially becoming the Batman of Kaladesh since his last appearance in Theros, complete with his own sidekick, who has taken the name Shadowblayde.
Chandra and Gideon Jura had even more build-up, including an implied romantic subplot in the novel The Purifying Fire. It makes for an interesting relationship, as they seem to like each other but openly despise what the other one stands for; Chandra being all about personal freedom, and Gideon about the importance of law and serving the greater good.
Garruk and Liliana: "I like your axe. Very manly."
The never-legal (and really unplayable even if it were legal) card Splendid Genesis◊, designed to commemorate the birth of Garfield's daughter, would qualify if it were ever played. He did, however, propose to his then-girlfriend, Lily Wu, over a game using Proposal. She accepted. (It did, however, take him four games to actually draw Proposal.)
Ho Yay: Nissa and Chandra have a number of close interactions, with Nissa opening up to Chandra more than to the rest of the Gatewatch and Chandra turning to Nissa for comfort and emotional stability. Furthermore, the Kaladesh storyline ends with Chandra sleeping with her head on Nissa's lap.
I Knew It!: Usually rare due to the many rumormongers who try to spoil each upcoming set, but the "priceless treasures" promotion from the Zendikar set qualifies.
Emrakul being behind the craziness in the Shadows over Innistrad block was widely predicted about as soon as the block began.
When people first saw Ixalan's Binding, they were quick to suspect that the Azorius and/or Ugin is behind Ixalan's anti-planeswalking lock. They were right.
Law of Chromatic Superiority: The Sligh Deck (named after Paul Sligh, who pioneered deck building mathematics needed to make it competitive) is known generically as Red Deck Wins for just this reason, although which color is the most powerful is a matter of fierce debate. In modern times, Blue is considered the most powerful, even following several years of deliberate depowering by the designers.
Yawgmoth, whose original, human incarnation is best described as "Hitler, but sexy."
Nicol Bolas, the oldest known planeswalker and the last Elder Dragon, is one of these. He's over 30,000 years old, has ruled empires, and is the Big Bad in more than one story. Currently, he's taken Yawgmoth's place as the current supreme threat to Dominia's safety and happiness, although in a more behind-the-scenes fashion.
Ob Nixilis is on his way to becoming one of these. A warlord who managed to ignite his spark after making a deal with demons that killed every living being on his home plane he traveled the Multiverse and conquered world after world, becoming a literal demon along the way, until arriving on Zendikar. Through the intervention of Nahiri, the lithomancer who originally helped trap the Eldrazi, he lost his spark and had his power sealed away due to a hedron placed in his head that also left him unable to leave Zendikar. Instead of giving up however he used the centuries he was trapped there to study the hedrons and the magic of Zendikar while manipulating any planeswalker he managed to come across until he finally tricked one into removing the hedron trapped in his head by claiming it to be the source of his power. The crowning moment of both his magnificence and his bastardry came when he interrupted the attempt to imprison the Eldrazi titan Ulamog by absorbing the hedron network's power to reigninte his spark and releasing the second Eldrazi titan Kozilek, but not before stopping anyone who got in his way in a vicious beatdown.
Meta Twist: In the Scars of Mirrodin storyline, Phyrexia has vastly superior forces, the element of surprise, and is the bad guy. Any player worth his salt would think The Good Guys Win against overwhelming odds, right? Nope. Welcome to New Phyrexia, folks.
Memetic Badass: There's a couple of average or bad cards that players like to jokingly say that they are the best card ever printed, but Storm Crow is the most (in)famous of examples. It's a blue 1/2 flyer for two mana. Seems fairly standard. Now, check the comments on the page.
"Symmetrical effects are fair and balanced" - sarcastically implying they're not, as the Game-Breaker status of Balance can testify. This is largely due to how one can construct their deck to minimize the impact they feel from said symmetrical effect.
"It dies to removal/Doom Blade/Murder" - sarcastically downplaying the strength of a very strong creature. Allegedly originated from a discussion over Serra Angel vs. Baneslayer Angel, where the latter is strictly better.
The flavor text for the Innistrad printing of Ancient Grudge is utterly Narm-worthy, and with the Spring 2016 set returning to the plane, it's gained a fair bit of notoriety.
If there's anything a werewolf hates, it's a collar especially Avacyn's Collar, the symbol of her church.
Avacyn hates fishermen.note The French version of the card Descend Upon the Sinful mistranslated "Sinful" (pécheurs) as "Fishermen" (pêcheurs).
The Yargle vs. Slimefoot debate during the Dominaria Launch over which was the most powerful card in the entire set. For context, Slimefoot took on an internet headcanon of being a "mushroom mommy" with its ability to create small tokens, while Yargle was seen as an invincible Commander- being a 9/3 Frog Spirit that... has no abilities. Wizard's Twitter asked the community what the proper response to an opponent successfully playing both cards. The overwhelming response? Scoop.
Moral Event Horizon: In over 20 years of media, Magic has as many pinnacles of atrocity as there are actual black holes in the universe:
During his exile, Yawgmoth visited several civilizations and ended up destroying them all with plagues he brewed up himself. In one case, he did it just to see what would happen.
Nicol Bolas and his corruption of Amonkhet. The people of an entire plane erased save for the infants; the corruption of its Gods; the perversion of the traditions of Amonkhet, all for the (so far known) purpose of creating an army of powerful undead to serve him on later conquests.
Nahiri might have been justified in feeling betrayed by Sorin. However, her revenge was ultimately the genocide of an entire plane by Eldrazi assimilation part of which resulted in the angelic guardians of the plane turning into twisted monsters slaughtering those they once protected, a gravity that has had them described as the biggest victims of Shadows over Innistrad just to get at one person. This moment was pivotal into turning her into a Fallen Hero.
Narm: The titular Magic Story of the Oath of the Gatewatch set. Gideon, you can see two mountain-sized Eldritch Abominations from up here, is now really a good time to swear your fealty to protecting the multiverse?!
The Eldritch Moon spoiler story for June 20, 2016 has the people of Innistrad getting corrupted by Emrakul, which is scary and disturbing enough until they start tacking Emrakul's name onto every other word in their sentences. Kind of hard to take the situation entirely seriously when people are saying things like "I'mrakul! We are'mrakul!"...
Narm Charm: "Ach! Hans, run! It's the Lhurgoyf!" is redundant, goofy, out-of-the-blue, and offers absolutely no explanation about what a lhurgoyf is.
Ixalan as a whole. Yes, it is a plane designed for your inner twelve-year-old, with dinosaurs, pirates, merfolk, and vampire conquistadores duking it out in over-the-top ways. Yes, it's still awesome.
Rescued from the Scrappy Heap: Atog was a scrappy thanks being the most printed card other than basic lands for a few months after Revised, but by the time Mirage made atogs an iconic race, not only had the haters disappeared in a puff of apathy, but the people who liked the atogs' goofily-large toothy grins and power in decks built to feed them were more plentiful than ever.
Mark Rosewater is the head designer and is essentially the public face of Magic design and development. If something goes wrong, it's his fault. Even if he had nothing to do with it, it's always MaRo's fault. People often mistakenly call him the head of Magic R&D as a whole. The game's inventor, Richard Garfield, seems to have escaped this.
Banding. Banding is easier to understand than "bands with other" and many times more versatile, but it's still complicated and unintuitive, and has been the butt of many jokes over the years as a result.
"Affinity for artifacts," although often acknowledged as a fair mechanic in a vacuum, gained infamy through its association with the "Ravager Affinity" deck that dominated the format at the time, so much so that its key cards were banned from tournament play. The backlash was strong enough that when Scars of Mirrodin revisited Mirrodin, the designers chose not to bring it back in fear that its new incarnation would inherit the Scrappy legacy of the mechanic.note Source.
Cards that require a coin flip have consistently been among the least popular cards in their respective sets, according to Wizards of the Coasts's market research. Head Designer Mark Rosewater explains.
Countering. A countered spell or ability simply fizzles. All the cost of it must still be paid (and sometimes, that's much worse than just mana), but the user gets nothing. This is very frustrating and the methods to get past it are rarely obvious to new players. This is a big reason the scrubs mentioned below say "no blue". In fact, countermagic is so unpopular that R&D has deliberately been reducing its effectiveness.
Land Destruction, or land removal in general, even if temporary. Due to land cards being of limited supply in any given deck, and that players must get those lands to actually play their cards (a major problem for any unlucky player), plus that normally a player may only play one land card per turn, destroying those lands will render a player having to wait several more turns to regain their land cards, by which time the opponent will have already have far more lands to play their actual game-winning cards without opposition. Similar to countering above, and perhaps to a much greater extent, land destruction as a mechanic has been significantly reduced in number and effectiveness, with more emphasis placed on destroying or otherwise nullifying nonbasic lands.
Ante is the worst one by far. It was removed a long time ago for running afoul of gambling laws, but even without the legal troubles, the single most common House Rule was "no ante", so it would have been scrapped for the hate alone anyway. Searching Blogatog for "ante" shows pages of posts like this one:
Q: which is more likely in a supplemental product: ante or bands with other?
A: Neither, but if I have to pick one, bands with others.
The Nephilim cycle of creatures not being legendary is a major irk to a lot of EDH players. While Awesome, but Impractical in every other format, their large colour spread and bizarre yet powerful effects would make them a perfect choice for a commander if only they were legendary. "Legalizing" them is one of the most ubiquitous house rules among groups, with many wishing that Wizards would simply say "screw it" and errata them already. Somewhat mitigated by the 2016 Commander supplemental set releasing five decks with four-colored legendary creatures.
Devoid is considered to be one of the larger missteps Magic Design has taken in recent years. The keyword makes certain Eldrazi-related cards colorless, despite still needing colored mana to be cast. While such cards can be noteworthy for some specific deck types, the set it was introduced in, Battle for Zendikar, had insufficient support for those sorts of interactions, so the keyword was seen as a mechanic that doesn't do anything. It has since become one of the go-to complaints about the block.
Scrub: As always, in contrast to the "Stop Having Fun" Guys: any card that the Scrub's deck can't deal with is "cheap", and anyone using it is trying to ruin the game for everyone who wants to play real Magic. It's common for people seeking casual games in Magic Online to put something similar to the following in the description:
No blue, no land destruction, no goblins, no elves, no nonbasic lands...
"Seinfeld" Is Unfunny: New players may be mystified as to why certain famous/infamous cards have such a reputation. Sometimes this is because of their still immature grasp of the game, but other times it's because those cards were simply good in their particular metagame, making their dominance a matter of context. Or even that the rules of Magic have changed so that whatever made them good in the first place doesn't work anymore.
"Stop Having Fun" Guys: As strong a force as the scrubs. Usually found battling against anything perceived as making the game easier.
So Bad, It's Good: A handful of cards, particularly from early sets such as Legends, are so thoroughly useless that they're regarded with a degree of affection by players. Chimney Imp, for example, is a particularly iconic one, attaining a status of Memetic Badass on the official forums.
Squick: Uktabi Kong, a card (tap two apes to produce an ape token) which invokes a number of sex tropes, but especially:
Yawgmoth's cure for phthisis actually worked, and his rant about the Thran cheerfully using magic they only barely understood for everything made a lot of sense.
Phyrexia, be it New or Old, is an entire plane of condensed Nightmare Fuel, and are the archetypical capital-E Evil faction of the game. They also have incredibly powerful magic and magitech due to their scientific approach to understanding the multiverse.
"Banding" and "Bands With Other" were so complex that they are among only a stark few keywords that they simply stopped printing entirely.
"Phasing" as well, due to the unusual and unintuitive ways that it works (permanents phase in or out on each of their controller's untap steps, and the rules have changed multiple times as to whether this triggers "enters/leaves the battlefield" effects or not. Currently not.)
There's also the rules about continuous effects and layers, which are relevant in every format and even more complicated.
To a certain extent, regeneration. In practice, it does just what it sounds like, but for technical reasons, it has to do it in a really weird way, which might cause unintuitive interactions. The complexity on what it can and can't do and how it interacts is why it has been retired from recent printings.
"Protection from X" has a fair bit of detail as to what it can and can't prevent, on top of what happens to creatures that suddenly receive protection temporarily. It will take a while for new players to fully grasp it, and its complexity has led to protection become increasingly rare in recent sets, usually being replaced with the more intuitive hexproof and indestructible.
Ante. It required all players to put a random card up for offer in order to raise the stakes, with the victor getting whatever cards were placed. Not only was it an extremely unpopular rule among players, since said card might be extremely valuable, but it had to be removed because of how ante could be considered gambling.
Technician vs. Performer: One of the oldest ongoing disputes amongst competitive Magic players is whether netdecking or not is more "pure". Netdecking is the concept of taking a well performing decklist, and fine-tuning it to your meta. The alternative being to develop a rogue strategy specific for the anticipated metagame.
They Changed It, Now It Sucks!: Too many times to count. Examples include the rules changes introduced here, but the game has to tweak itself a little every year, and each year brings a plethora of complaining, along with the beeping of cash registers to drown them out.
The major rules overhaul with Sixth Edition caused a massive outcry among players at the time.
Perhaps the biggest Internet Backdraft occurred in 2003, when they made some rather drastic changes to the cosmetic layout of the cards.
Four words: Planeswalkers as playable cards.
As of the M14 core set, both players may have a copy of a legendary creature. Cue cries of how this cripples clone decks.
The Jund deck that dominated Standard after the release of Alara Reborn.
Jace, the Mind Sculptor's unprecedented price tag (about $100 at its peak), combined with his status as a staple in multiple formats, has earned him a lot of unpopularity among some segments of the player base. It got to the point that Wizards had to ban Jace from decks.
This applies to the Homelands expansion. Almost all of the cards were too weak to see any play, even outside of tournaments, giving it a reputation as a set consisting of nothing but useless junk (The Duelist once admitted the only worthwhile card in the set was an ok anti-weenie card, and people only played that when there were block rules that required decks to contain cards from every expansion in the current rotation; later, Merchant Scroll gained some popularity as well). Packs of Homelands cards were still available in stores for next-to-nothing long after it had "officially" gone out of print. Player reactions were so poor that in 2006, it was retroactively replaced in the Ice Age block with Coldsnap.
Fallen Empires, too, for about the same reasons. Although it did have several cards that saw tournament play, its best cards (such as Order of the Ebon Hand and Hymn to Tourach) were common, so players didn't need to open many packs to collect all the cards that they actually wanted. It was also massively over-printed, with almost six times as many cards printed as any expansion set before it (approximately 350 million cards, compared to the 62 million of the preceding set, The Dark) and almost as many as the then-current base set, Revised Edition (estimated at 500 million cards over its lifetime.) This imbalance between supply and demand kept the price of Fallen Empires packs very low for a very long time.
After the overpowered Urza's and Rath blocks, Mercadian Masques block was deliberately underpowered to help re-balance the game. Unfortunately, the result was a weak block that did nothing to stop Rath and Urza from dominating competitive play, and its popularity dipped further after the premiere of the following Invasion block, a fan favorite that changed the metagame without being broken.
Even worse, bland mechanics and character designs meant it just wasn't fun. One big problem with Mercadian Masques was all the reprints of weak cards. (Kyren Glider < Goblin Glider, Moment of Silence < Festival, the return of storage lands from Fallen Empires.)
Kamigawa block tried to do the same thing after the the insanity of Mirrodin, and fared about as well. It was followed by Ravnica to boot, a reasonably powerful set that's been a fan-favorite since printing (even the less powerful cards are considered fun).
Too Dumb to Live: The writers of the Guildpact, for intentionally writing in an antagonist for whom failure was NOT the only option, because "hey, there's an empty slot." The spoilered mistake sets in motion the plots of the entire original Ravnica trilogy.
Trapped by Mountain Lions: In the Innistrad block story, Sorin Markov is waylaid by Tibalt. This occupies him for the entire arc, thus contributing nothing to the situations around Avacyn's disappearance (which is very bad news for Innistradi humans) and her subsequent release from the Helvault.
Underused Game Mechanic: Transform, originally introduced in the Innistrad block— essentially, cards that transform have rules text and art on both sides, and have certain conditions to change into these forms, and possibly change back, in the case of werewolves. It's a distinctive mechanic that brought a lot of identity to Innistrad— the lack of it in Avacyn Restored is often cited as to why it's considered disappointing. It returned in the Shadows over Innistrad block, And There Was Much Rejoicing. It's started making appearances outside of Innistrad— several cards in the Ixalan block could transform into lands.
Villain Sue: Nicol Bolas is often accused of being this. While the other villains (including the most popular ones) are powerful and sometimes victorious, they do share the spotlight and are known to have relevant weak points — even the Praetors, who are currently controlling Mirrodin, are lacking in unity. Nicol Bolas, however, is being shoehorned everywhere, always getting the upper hand, becoming oh so monstruous without much Character Development and turning out to be the mastermind behind each and every machination taking place in the Multiverse, to the point that his involvement has become The Untwist for many.
When the Odyssey block first came out, many players complained that it was underpowered and too focused on the graveyard. Since then, several of its cards have become staples in Legacy, and it's appreciated for introducing the idea of the graveyard as a resource.
The Kamigawa block was much maligned at launch for being underpowered compared to Mirrodin, as mentioned above. However, it has more legendary creatures than literally any block in Magic history, and with the rise in popularity of the Commander/EDH format (which requires a legendary creature to be your deck's commander), its legends are being looked towards as viable in this format. The Japanese folklore- and mythology- inspired flavor has also gotten praise.