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.
The Fantasy books
Squick: Kane having sex with Efrel in Darkness Weaves.
The Untwist: In Dark Crusade, the evil god's dark prophet has amassed an army of fanatics. They march to face a vastly superior force of well-armed, well-trained knights and soldiers. The knights are naturally confident that they will easily defeat this rabble. The reader holds his breath in anticipation of some dark magic that will turn the tide for the fanatics, but it never materializes, and the dark prophet's horde gets stomped.
Badass Decay: Some will point to the Katie Vick angle as an example of this - and it certainly counts - but most will point to a single moment: when Kane lost his mask. Many fans feel he's never recovered from this.
The moment itself is being treated as Canon Discontinuity by WWE these days. In a recent storyline Kane stated that he was unmasked by The Undertaker (though he was unmasked by the Undertaker at Summerslam 2000 before his permanent unmasking, he put the mask back on afterwards).
Remember, the person who said Undertaker had unmasked Kane was Kane himself, and in kayfabe, Kane's always been a little...unbalanced. So Kane could have convinced himself that it was Undertaker who caused him to permanently unmasked, even though it was actually Triple H who was the mastermind behind the unmasking, because he hates Undertaker that much.
In an interview, Glen Jacobs claimed that the only people 100% behind the unmasking were Vince McMahon...and himself. He felt that they had taken the character as far as they could behind the mask, and that the addition of facial expression allowed him to add more depth to the performance. He also noted that it was becoming increasingly uncomfortable and difficult to wrestle with the mask on, and that removing it was a relief.
Really, aside from the Special Effects Failure, the unmasking itself wasn't a problem. In the months immediately following the unmasking, Kane committed such acts as throwing Rob Van Dam (his friend at the time) through a steel cage, setting Good Old J.R. on fire, tombstoning Linda McMahon, electrotorturing Shane O'Mac's testicles with a car battery, beating Shane in the first ambulance match by tombstoning him on the concrete floor, and burying the Undertaker alive. He sent the whole faction of Evolution running scared from him when he made his entrances. The problems started when they put him in the world title picture for all of a month so he could destroy Goldberg so that Triple H could beat him; after that, they didn't have anything for him to do up until the Royal Rumble where they started teasing the Undertaker's return, and from that point it was only a matter of time until he was used to worf to the returned Deadman. Once that storyline was out of the way, they didn't have any idea what to do with him, and it all went down hill from there.
Crowning Music of Awesome: "Slow Chemical", Kane's entrance theme for years after he'd gotten unmasked (and for a while prior to the unmasking).
His first theme went well with how his character debuted, and his newest theme sounds a bit like his first theme without the guitar riff. Both are awesome.
Designated Hero: Kane often turns face by default only because the person he's feuding with just happens to be an even bigger heel. Certainly the most prominent (and questionable) example is his feud with Edge over Lita, in which his characterization would be summarized as "Vengeful, jilted rapist." And he was the hero...if real life didn'twrite the plot, WWE even coming up with this would've backfired unless the intention was to double-turn Edge and Kane rather than make Lita heel. Lita turned into something of a Designated Villain for walking out on her abusive rapist husband.
Designated Villain: Turned heel on the Undertaker right before Summerslam 2000, since UT's original intended opponent, The Big Show, had been shipped off to WWE's then-developmental league Ohio Valley Wrestling in hopes that he could lose some weight. While the turn was a surprise as far as Kane's character direction at the time, at least it was understandable why Kane might still be mad at UT.
First Installment Wins: Kane as Taker's insane, evil younger brother who supposedly died when the family funeral home burned down when they were kids but somehow survived and came back for revenge, with other acts of mayhem and destruction along the way? Great. Kane after a bazillion nonsensical Retcons, jobs to [[Shane Mc Mahon Shane McMahon], losing the mask, talking like a normal person, and other WrestleCrap: Not so much.
Fridge Brilliance/Visual Pun: He does look an awful lot like Orson Welles in Citizen Kane, particularly Charles Foster Kane in his later, "Rosebud" years. His political blog, "The Adventures of Citizen X", takes it even further; if you take the X as a variable, it becomes "The Adventures of Citizen Kane".
Also, it's an inversion of the Biblical story, where Cain kiled his brother Abel.
Magnificent Bastard: Revealed himself to be this after using both the feuds and times he teamed up with The Undertaker for over a decade as a way to exploit his weaknesses and then playing the role of the avenging brother in 2010 all the way to the World Heavyweight Championship. (see Xanatos Roulette on the main page)
Special Effects Failure: This has happened to Kane a number of times over the years; sometimes it's been a part of an angle, sometimes it's been a legit malfunction. His unmasking is probably the most notable one, as the supposed 'burns' on his face ended up looking like smeared makeup (which it was). It had to be distorted in later promos to make it look scarier.
He was suffering from severe Badass Decay even prior to his unmasking. One needs only refer to any incidents that could be classified as Crowning Moments of either Funny or Heartwarming that occurred while he was masked. For example: the 'Kane-o-roonie'. The friendship with X-Pac. The relationship with Tori. (Both turned on him and lived to tell about it.) His first words being "Suck it" - the D-Generation X catchphrase. Tag teaming with the Hurricane and saying "Freaks are cool!" Many feel when he started talking (i.e. acting more and more human), he lost his threat level.
Worth nothing that it was Kane's decision to lose the mask, as he said it was becoming more difficult to wrestle with it on and that he felt limited with the character since he had to convey emotion with just his body. According to reports, only Vince McMahon was fully on-board with the change, but if there's one guy you need to sign off on an idea...
Also worth noting is that while even though it was incredibly unpopular even at the time, the unmasking did a lot to undo his Badass Decay; it wasn't until the Royal Rumble the following year where they started building up the return of the Undertaker, who Kane would eventually job to at Wrestlemania XX, that the decay began to set in again. For several months before that, Kane was nothing but an unstoppable monster.
Just when he was becoming a Badass again, the recent storyline in which Paul Bearer is abducted by Edge has managed to decay it all over again, with Kane insisting he's a human being with feelings, and that he loves the holidays and just wants his dad back.
It also just smacked of desperation, since he was beginning to sense Edge was just continuously one step ahead of him.