Badass Decay: In his first appearance Bismarck was able to hold his own against Suzaku, Schneizel and Cornelia all at the same time. Come the Grand Magic Games, he gets his ass soundly handed to him by Asura, Shimon, and Erza.
Somewhat mitigated by the the level in Badass these characters have taken or the breath their capabilities. It less a case of Badass Decay and more a case of Menace Decay Bismarck is just as strong now as he was at the beginning, but the addition of much stronger characters, not too mention all major protagonists Taking a Level in Badass has turned him into a elite mook.
Thanks to the increased power scale of certain characters and the addition of new powers which can counter others from canon, several canon characters are munch lower in the rungs than in canon. A standout example is Lyon who was a case of Always Someone Better than Gray when it came to Ice make, but is a case of Can't Catch Up in this story.
Sting and Rogue zig-zag this, they tend to perform better than in canon, but have less of a reputation thanks to the exponentially higher power curb in-story.
Blue Pegasus treatment is a Subversion. They actually are stronger than in canon but are only strong enough to retain their Butt Monkey status among major guilds.
Natsu. Many fans are upset that he's winning fights that he shouldn't be able to win, especially with Lelouch losing some of his fights. Some even accuse Natsu of having a case of Spotlight-Stealing Squad. Others think the fans need to take a chill pill and are open minded to the writer's attempts to re-invent Natsu into a more interesting character.
Kagura and Jellal as a pairing has left fans divided. Some believe it's much better and well-developed than the canonicaly implied Erza/Jellal, while some believe it's ever worse.
While Mordred as a character is a class example, a decision regarding the character split the fanbase and even gave the author pause. As it later turns out, Mordred is the name of the demon within Future Lelouch and nudged him into doing reprehensible things, thereby lessening the impact of seeing Lelouch at his darkest. The author even acknowledges this drawback, defending that he feels the pros simply outweigh the cons, even finding that he made Lelouch too evil. Of course, his fanbase is split on this.
The Guild War has caused this for munch of the fandom. Specifically between those who feel it's fine and enjoy the battles and conflict between Lelouch and Suzaku. Others feel that the arc is really nothing more than an Idiot Plot where Suzaku is once again thinking without sense and letting VV get away with everything and think that the overall war is very one sided in terms of strength. the Fairy Tail and Knightmare Frame alliance and allies to be specific.
Dork Age: The Cracked Gemstone Arc is viewed by this by much of the fandom. Much of the arc can be described as Lelouch crying like a bitch into Erza's lap and her comforting him in ways that are out of character or Lelouch angsting and needing to be told he is awesome to overcome his conflict over being Zero. The arc quality is also not helped by the fact that the arc ultimately ends in a Shaggy Dog Story where all of Lelouch's actions in this arc came to nothing and no new information of the main plot or Myth Arc was revealed making the arc come off as padding. Its rather vicious Kill 'em All of the titular group elite was seen as particularly brutal compared to several far more nasty characters in the series. It's seen as the author being quite petty to who they were expies of, which he makes no attempt to hide as he freely admits to being quite bitter. It's especially bad since many fans feel that those characters weren't developed enough or came off as undeserving of such brutal fates. Many see the only good thing about the arc was it lead to chapter 208.
What causes further contention for this arc is how some fans are starting to think Lelouch is becoming more and more of a socipathic hero with many of his actions and reactions to events: such as the killing of Ember without even listening to her reasoning before killing her and his total apathy to the complete slaughter of cracked Gemstone elite. It makes Lelouch come off as very unsympathetic.
Ensemble Dark Horse: Sindel and Airy are well-received by the fan base at large, even voting them into the Fairy Tail Team B for the Grand Magic Games more often than some of the canon cast members.
Emma Jaeger is also a very popular villain due to her status as a Wake-Up Call Boss during the Sindel arc and the first-non Arc Villain to give elite members of Fairy Tail trouble. Even in her subsequent appearance, she doesn't suffer a case of Badass Decay and it's still tough to take her down. Fans can't wait to see her come back. In fact her entire involvement in the Envoy of the Future arc is described by Draconic Hero as Fanservice since he had no intention of originally putting her in the arc until fans asked for her.
Enna Elsa was quite a hit when she had her first serious appearance. Being a hilarious TrollMs. Fanservice type character and strong enough to completely hand Natsu his ass without trying certainly helped.
Foe Yay: Rakshata and Lloyd are still trying to one up each other. Laxus and Gajeel even comment to the effect that they should do the sideways polka. Hilariously enough they do have sex in one chapter, but refer to it as an experiment.
sadly further information from 514 ruined the author first set of plans and depending on canon could have major repercussions for the later arcs in the series. The Author does have plan and is waiting for canon to make him decide on what is the best move.
With the release of 515, all that was ruined by 514 and 513 has now made this a complete subversion and not only does the author plan to use Irene, but plans to turn her into the Big Good. see here.
the reveal of Acnologia element in canon has made Mordred entire goal and plotline this. specially Mordred forcing Lelouch to absorb the element of every dragonslayer in Fiore to be able to counter Acnologia. 528 reveals, however that Acnologia doesn't use any specific element but eats and uses magic itself as his power, so no matter how many elements mordred collected. His goal was doomed to failure; meaning everything Mordred did, from all the lives taken, the pain and misery of the victims friends and family not to mention lelouch own emotional strain would no matter what have been All for Nothing in every possible outcome.
The Author stated in the AN at the end of chapter 59 where it was revealed Morrigan is Zeref sister and his statement about Zeref probably not having any siblings in canon becomes this. On account of the fact that he does have one.
If the writer is to be believed, he had the scenes with Juvia and Gray in Gildarts' summer home planned out far in advance, making the scenes in the Avatar arc an example of this trope.
Larcade being Zeref and Mavis son in canon has made the fact that Zeref is very likely Mavis husband this. Including the fact that they had a child who would eventually carry on the line to Lelouch.The Author has even stated that this revealation has forced his hand into making the relationship canon in FWW.
While there's nothing exactly funny about Margaret by any stretch, she was still a mom of a canon character, incredibly powerful, and a villain. Enter Irene years later in canon who is almost a canonized Margaret if not for her Dark and Troubled Past that make her more of a Tragic Villain, while Margaret was created with no such redeemable qualities in mind.
Yamato Hayabusa Having God soul is this since the author had this planned long before a character who wielded the power was revealed in canon.
While the possibility of turning into a dragon was well known since the Grand Magic Games arc, Natsu bypassing Igneel's seal and turning into one in this fic has become funny in hindsight the moment it was revealed it will probably happen in the movie Fairy Tail: Dragon's Cry.
Ho Yay: The author wasn't even trying to be subtle with the scenes between Orochi and Hibiki at one point describing Hibiki stripping in front of Orochi as an uke giving into their demanding seme.
Female example: Kallen and Sachi certainly had their moments...even if they lasted for all about one chapter. Nonette and Cornelia get this a lot and even Milly and Shirley have a touch of this. Right now Nina seems to be one-sided regarding Euphemia.
This is taken to its logical conclusion Up to Eleven in Mermaid Heel.
On the subject of Mermaid Heel, fans have started to cry for Tamara from that guild with Legretta from Phoenix Grave as a potential pairing.
Like You Would Really Do It: As if anyone expected that Erza jumping in front of Acnologia's attack would actually get her killed off, thereby sinking the driving ship of the narrative between her and Lelouch.
Moral Event Horizon: Many reviews for chapter 193 followed a pattern of "any sympathy I had for Mordred went out the window for attacking Nunnally" doubly so given that Mordred is Lelouch from the future.
The Scrappy: Suzaku's Lawful Stupid nature in chapter 74 has made him this to a lot of readers. Some Suzaku haters have even said that they hate this verison more.
while very strong among some members of the fandom. He has slowly but surely been getting out of the Heep. Him becoming the benevolent and competent guildmaster of Sabertooth. Which was the author attempt to accomplish this was a definite help along with his romance with Minerva is seen very well done, citing Character Development for both as a major reason. Some actually find thus romance much better and believable than Erza and Lelouch, which many saw as predictable, but still rooting for tends to make both act out of character and has no real development or drama for both.
Ships That Pass in the Night: While the ever popular Lucy and Lisanna debate over Natsu is backed by the first letter of his future wife's named being L, Phoenix Grave mage, Legretta Upton is gaining traction. This is because she and Natsu are similar in terms of personality, fighting style and determination. And this is in spite of the fact that the two have never interacted with each other once since Legretta's introduction.
They Wasted a Perfectly Good Plot: The Fake Zero in the Cracked Gemstone arc. What many saw a good way to see some negative percussion of Lelouch's actions and persona as Zero were just used as a background detail and justification for Lelouch to kill Ember. What makes this particularly grating is the fact that this detail was overall useless to the arc as a whole and removal of would likely change absolutely nothing.
What an Idiot: Sometimes the more...innocent characters of the series can drive you to facepalm
Euphie, sweetie, being in a relationship with someone isn’t going to stop the Male Gaze
NINA! YOU FUCKING IDIOT! Euphie had the situation with Kallen under control!
Estellise has so many that we’d be here all day listing them.
The Woobie: Outside of Knightmare Frame you have Undine Celeste, the guild master of Mermaid Heel who was taken in by Erubay, the water dragon. Erubay, an otherwise humanhating dragon, took her in and raised her, but when Undine ran off after discovering another human, eventually being asked for her hand in marriage, Erubay killed her fiance and Undine became so enraged that she wound up killing her own mother. If that wasn't bad enough, since she doesn't have the dragon anti-bodies that were given to the other dragon slayers in canon, she is slowly turning into a dragon and her arms are the first victim on her body. She has also regretted that day of her life for the last 23 years and counting. At least one reviewer of the story has admitted to wanting to give Undine a hug.
Basil Fernandez. Check the spoiler tab for his parents. Just being born to that woman is enough to be this. Suppose we should be thankful CC somehow got him out of there.
Woobie, Destroyer of Worlds: Sindel becomes this in hindsight when one looks back at her first appearance. Sure, she's going on a massive rampage and flattening everything in sight with her destructive power, but deep down, she just misses Mavis and her warpath is constructed purely out of the wounds of what she considers Mavis' betrayal. It's even pointed out that, in spite of her wrath, she's still a Fairy Tail mage at heart.