These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Base Breaker: Monica. Some fans hated her, while others thought she had an awesome super power. The main problem with Monica was that she was involved in a Trapped by Mountain Lions plot, so all her powers were a waste.
Sylar is the epitome of this trope. You either love or hate the mayhem he wreaks on everyone.
Best Known for the Fanservice: Particularly that provided by a certain adopted self-healing cheerleader, an idealistic nurse, and a watch repairer with serious parental issues.
Better on DVD? Though some say watching it on DVD makes you much more aware of the myriad of plot holes and aborted arcs and inconsistencies that watching it slowly one week at a time would eliminate.
And that ended up shooting them in the foot once Sylar made a solid Heel Face Turn.
Ensemble Darkhorse: Claude, Ando, Elle, and even Mr. Muggles have fanbases. In the first half of the first Volume, Hiro was like this too - then the producers listened and gave him an increasingly larger role. Minor characters from the Graphic Novels such as Linda Tavara (Who only had three appearances, total) have sizeable fanbases. The most extreme example is Sparrow Redhouse who, despite only appearing in 3 panels until recently, was a character many wanted to see on the show.
Fixer Sue: Matt Parkman Jr. seems to have solely been created for the purpose of giving Hiro his powers back and getting Matt back with Janice (even though the latter was universally hated)
Foe Yay: Where to begin... Mohinder/Sylar, Sylar/Peter, even, in a disturbing way, Sylar and Claire in the Fourth Volume finale (and in the later episodes of Volume Five). Sylar's just sort of a Foe Yay whore.
Sylar/Chandra belongs here too. "Hello, Chandra. Why won't you talk to me? You can't leave me like this."
It can be argued that this might be invalid, as they did have a prior romantic relationship before his Startof Darkness drove him over the edge. Still, he didn't seem to recognize her at the end of Powerless and she got really pissed when he murdered her father.
Sylar gets a lot of enjoyment out of making Angela uncomfortable as possible, even to the point of kissing her while voicing death threats at her.
We can safely add Sylar/Danko to the list, if only because Sylar seems to enjoy impersonating Danko a little too much. Sylar really is a Foe Yay whore.
...Sylar uses his new shapeshifting power to pretend to be Bennet's wife.
Adam/Hiro and Adam/Peter goes here too.
Adam (to Hiro): You were more than a friend to me...
Hilarious in Hindsight: In-Universe: In "The Fix", Claire is looking for her biological family, and Zach suggests hopefully that she might have a rich, eccentric uncle. "Great," quips Claire, "an uncle."
Also Zach was supposed to be gay but this was not made known to Thomas Dekker. He would later go onto play a gay character in Kaboom!.
"Save the Cheerleader, Save the World" itself because Claire ended being the key driving force in saving the world from Samuel in Season 4.
All the Sylar-related Ho Yay became this after Zachary Quinto came out.
Nathan and his ability to fly, after it's revealed that Adrian Pasdar is now the voice of Iron Man, a hero who can fly.
Idiot Plot: Although it had been passed around freely between the characters in Volume One, by the time of Volume Two, the writers appear to have grasped the Idiot Ball firmly, with the result that the premature conclusion to that arc almost feels like a mercy killing. Volume Three was even worse, with a promising plot involving twelve escaped villains and the return of Adam Monroe scuttled in favor of the introduction of Voldemort-wannabe Arthur Petrelli and a series of nonsensical subplots best not mentioned.
The Finale of the show had the Evolved Humans be outed by Claire on National Television. Claire, you've seen several dark futures and seen what people do when they find out about your abilities... what made you think this is going to end WELL?
In fairness, present-day Claire doesn't know about these dark futures as she's never traveled through time to the futurenote though she has been to the past, nor does she have any Isaac Mendez-type foreseeing ability.
Except that she has been present and has knowledge that The Company abducted and imprisoned those with powers, as did Pinehearst, not to mention that Nathan had conspired with the President to lock up evolved humans. It's obvious which way this would inevitably go...
Well, it was kind of inevitable that the outing would happen (like Sylar said, it's a brave new world). At least we were spared a fifth season finale with Hiro travelling back in time and heading Claire off at the pass.
Incest Yay Shipping / Incest Subtext: The Petrelli brothers are unusually close despite their roughly 13-year age gap, and then when factoring in Claire, who is Nathan's illegitimate daughter, there's a lot of subtext. Didn't stop Milo (Peter) and Hayden (Claire) from briefly dating, though.
Logo Joke: When the series was shown on BBC Two in the UK, it was preceded by a special Station Ident in which the '2' symbol eclipsed the Sun, though it isn't part of the actual show.
Magnificent Bastard: And in this corner, the fight is between Bennet and Nathan Petrelli. Odds favorite is currently Nathan, as he manages to be a Magnificent Bastard even when the people know it. With the introduction of Mr. Linderman - who calmly managed to talk Nathan down - a new contender was on the field. And just when we thought Bennet was out of the race, he cranks it up to 11 and shows he's a bigger bastard than even we dreamed. And then there's Bob, and don't discount Adam Monroe yet... it's a veritable bastard battle royale! And don't forget Magnificent Bitch Angela Petrelli.
Samuel Sullivan is definitely one. If he wasn't one before, he became one the moment he pretended that he was about to surrender to Noah to atone for his crimes, only to have his flunky open fire from the shadows, wounding Samuel and killing at least one member of the Carnival (who had been about to turn on Samuel), leading everyone to believe that Noah had tried to kill Samuel even when he was prepared to surrender... and therefore making them a lot more willing to forget their doubts about Samuel and go along with his anti-Muggle agenda. Now, if that ain't Magnificent Bastardy, I don't know what is.
Don't forget Sylar either. His ability to manipulate his way out of every situation, play those around him and adjust to anything thrown at him is practically another superpower. Examples include impersonating a hero to get close to Mohinder, turning Matt Parkman's power against him, manipulating Danko into letting him kill and take powers, and tricking Maya and Alejandro to bring him to Mohinder.
Samuel has a killer one in "Once Upon a Time in Texas" - after spending the episode doing his utmost to save Charlie from Sylar, three years in the past, Hiro walks out to discover that she's been taken by Arnold, Samuel's time-traveling carnival member, at the behest of Samuel. Samuel reveals the entirety of the episode, including his previous attempts at goading Hiro into changing the past, have all been a manipulation to force Hiro to work for him, and to possibly prevent the death of Mohinder. Needless to say, Hiro is less than amused.
He hits a new watermark in "Pass/Fail," when he wipes a town off the map after getting dumped. He doesn't even have an excuse so much as he's just pissed.
From Bad to Worse: After the entire carnival loses respect for him, he wins it back by murdering Lydia and blaming Noah for it.
MST3K Mantra: It's often easier to enjoy the show for the lulz than taking it seriously.
Janice: whether it's for replacing Daphne in Season 3/4 or being a huge bitch to Matt in Season 1.
Snark Bait: There are entire LJ communities in which getting together every Monday night to watch Heroes - for the sole purpose of giving it the MST3K treatment - has become a ritual and a bonding experience. Wet Sylar, Carniawarts, Clairiett Tubman, Sylar Durden, Rainbow Brite Girl, Gretchward Cullen - we salute you.
So Bad, It's Good: The third season is like watching multiple train wrecks in superspeed. While on acid. Quite literally too, in the case of the ending of episode 3.16 ("Building 26").
Strangled by the Red String: Matt Parkman and Daphne Millbrook in Volume Three. Exactly what do these two characters have in common again?
Which she just acknowledged herself.
Actually, she didn't. She repeated the erroneous statement that Matt's vision was only a "dream." Not only did Angela see the same future, but Peter was actually *in* it. What she said was either 1) wrong or 2) a retcon.
The thing about this is it was actually well done and well-received.
The Woobie: Multiple characters get this treatment notably Hiro, Peter, Adam, Elle, Noah and Sylar.
Also attempted with Nathan Petrelli at the beginning of Season 2 (mostly by making him grow a truly horrificBeard of Sorrow) - a decision which pretty much led to a fandom revolt and was never referenced again.
The Adam as Takezo angle can be seen as racist and whitewashing as a white guy as one of Japan's greatest heroes? Not cool. Not only that, Japan in that time period was highly xenophobic...Adam would have been killed already for not being Japanese if he didn't have regeneration.
The treatment of female characters and characters of color, such as killing off Simone, Isaac, D.L. and others, as the story became more focused on the white characters with only small bits of story given to Mohinder, Hiro, and Ando.
The end of the The Fifth Stage has Nathan committing suicide to end the threat of Sylar. His body falls in the shape of a cross and church bells can he heard right after he hits the ground. Nothing symbolic there, no sirree.
What an Idiot: Eden. Did it not occur to her that if she could use her power on Sylar, he could use his powers, too?
Assorted character YMMVs
Ho Yay: With Peter, though YMMV due to the squicky implications.
Magnificent Bastard: Most impressive in Season 1. He certainly tries in Volume 3 & 4, but it almost gets him killed. Repeatedly.
Foe Yay: With Sylar and Elle (though more the latter than the former - she may have had a Cat Fight with Elle but it was Sylar who she stabbed in the stomachnote which would have killed him for good if he hadn't managed to get her power, jabbed in the skull with glass and plugged in the eye with a pencil).
Incest Yay Shipping: There was a huge surge in shipping her with Peter after the dramatic rescue at Homecoming, her being so happy to meet someone else with powers, and calling him her hero. This got hit with the power of hindsight later when it turned out that he was her uncle - which neither of them knew at the time.
Iron Woobie: Aided in no small part by her powers, Claire never gave up despite all the pain and suffering the world heaped on her.
Wangst: Boy, she was bad about this for a long time during Volume One.
Memetic Molester: Whether they want to or not, Sylar has sexual tension with everyone. Everyone.
Neutral Evil: Anything he does is for his own gain and validation. He doesn't care about the special round up, making a better world, or the plot to blow up New York, he just wants to cause mayhem and be the most special person on the planet. Just don't try to exploit his validation and parental issues. He basically considers lying to him the most heinous crime.
Villain Sue: Became an unstoppable, unflappable and unbeatable writer's pet around the time of Volume 2. This becomes annoyingly egregious around Volumes 4 and especially 5.
To be fair to the writers, he only turned out as such because fans loved him so much that they preserved him long after he was needed or wanted.
Better Than Canon: In a less outward way because he explicitly shipped Elle/Sylar by locking them in a room together where she could torture him to his pleasure. Then grounds Peter so that he needs to stop playing with the Idiot Ball, takes the resident Mad Scientist and gives him other people to experiment on... gave to good reason to get rid of Maya and her anthrax tears.