Complete Monster: The Betrayer, originally one of the sorcerers and seekers who helped found the Huntik Foundation, turned upon his fellows to summon the Lovecraftians monstrosities known as the Nullifers to destroy the world. The Casterwill family fought back and destroyed the Betrayer, but his spirit endured, forming the Bloodspiral Brotherhood to work at his revival. The Betrayer eventually had the Casterwill family "purged" with any who served as obstacles treated the same way. Upon his revival, the Betrayer revealed that he had double-crossed the Bloodspiral Brotherhood and they would not be spared from destruction either. The Betrayer proceeds to summon a comet the destroy everyone present and summon the Nullifers, plotting to destroy everything that lives on Earth to satisfy his lust for chaos.
Nightmare Fuel: The two Blood Spiral-only spells, Darkvoid and Abyssalfall, which essentially create localized-yet-temporary black holes, and all that implies - the former is inescapable, while the latter can be escaped from with help, yet is still dangerous. Most of the targets are inanimate objects and/or Titans note Their amulets are destroyed if successful, but it's ambiguous if they're truly dead or merely returned to the Titan World., but in Season Two a Silent Soldier used the latter spell on Sophie from behind... without the last-second save that followed, the result couldn't have been pleasant.
Replacement Scrappy: Den is seen as this by some, especially Zhalia fans, who felt that Zhalia's infiltration subplot was unnecessary and a mere excuse to get rid of her and put him in her place as the fourth member. In the epilogue of Season 2, he takes Dante's spot, when he's promoted to the Huntil Council, and Lok becomes the new team leader.
The Scrappy: One or two people may not like Cherit. Heck, it almost seems like Cherit was designed to be this, but despite his nails-on-blackboard voice and shrimpy appearance, he's actually pretty funny and likeable. Plus, y'know, lasers.
What an Idiot: Subverted. Zhalia reveals herself the mole of the Organization and beats the crap out of Lok and Sophie. She's about to finish them off, but instead ties them down, saying she'll be back for them later (which looks like this trope). The initial plan was to kill them, but she ultimately couldn't bring herself to hurt them, and so she tied them down while her mind's in turmoil, enough that they could escape- having to hurt Dante was the last straw that turned her to their side, while Lok and Sophie do indeed escape.
The Woobie: Zhalia, after her backstory is revealed. In season two Den, Harrison, Dante, and Sophie all have these moments.