Creator Killer: Thanks to the mostly disliked or simply indifference-inducing ending, many fans have stated they'll have a hard time reading another story from Matsuri again, if they'll read it at all, fearing she'll just create another one with messed up morals and/or another trolling Love Triangle. The fact that the magazine in which Vampire Knight itself was published in made Matsuri cut the story because it wasn't popular enough anymore doesn't exactly help.
Executive Meddling: Sales dropping ever since the start of the second arc eventually caused the magazine LaLa to force Hino Matsuri into cutting her ending, apparently even three times. As a result, Matsuri even publically apologized to her readers in her blog for the ending being as rushed as it was, being sorry she wasn't able to tell the full story she wanted.
I Knew It: Yuuki is a pureblood vampire. This was somewhat easy to see coming, but the exact manner was still something of a surprise.
Many fans predicted that Kaname would be alive at the end despite all the foreshadowing of his death.
Talking to Himself: Mamoru Miyano (original) and Vic Mignogna (dub) voices both Zero and Ichiru.
Trolling Creator: Hino Matsuri being a rather infamous example for her Love Triangle's antics, the epitome of her trolling probably being towards the ending where Yuuki kisses and admits to being in love with Zero in one chapter... and then sleeps with Kaname two chapters later (merely one week later in-universe). She then has a child from both guys in the end, and the love triangle itself is also left with No Romantic Resolution.