Grimmel

Grimmel the Grisly is the main antagonist of the film How to Train Your Dragon: The Hidden World. He was a dragon hunter who believed that dragons must be exterminated, and was responsible for bringing the Night Furies to near extinction, leaving Toothless the last one of his kind.

In HTTYD 3.
One year after the events of the previous film, Hiccup, Toothless and their fellow dragon-riders continue to rescue captured dragons in order to bring them to Berk and its bustling dragon and human utopia. Their efforts have resulted in the island becoming overpopulated with dragons. In a response to the overcrowding, Hiccup desires to find the "Hidden World", a safe haven for dragons spoken of by his late father Stoick. Meanwhile, a white Night Fury dragon, held captive by the warlords, Chaghatai Khan, Ragnar the Rock, and Griselda the Grievous is given to infamous dragon hunter Grimmel the Grisly as bait for him to capture Toothless for the warlords' use as an alpha.

Toothless discovers the white Fury (dubbed a "Light Fury" by Astrid) in the woods and the two become enchanted with each other until the Light Fury, sensing Hiccup's nearby presence, flees. Hiccup and Tuffnut later discover Grimmel's dragon traps in the area. Grimmel visits Hiccup that night, but Hiccup has prepared an ambush to capture him; Grimmel escapes, burning down Hiccup's house and part of Berk in the process. In response, Hiccup rallies the citizens and dragons to leave Berk on a quest to find the Hidden World and safety from dragon hunters.

Mid-journey, the Berkians discover an island on which they initially plan to rest for a short while, but soon begin to settle there, even if only temporarily. Seeing Toothless's inability to fly solo hindering his growing relationship with the Light Fury, Hiccup rebuilds an automatic tail for him. Upon receiving the tail, Toothless flies off, meeting the Light Fury on his own and flying with her to an unknown land. Valka, on a scouting patrol, notices Grimmel's approaching army and quickly reports back to Hiccup. Hiccup and the dragon riders head to capture Grimmel; yet, they fall into his trap and barely escape. Ruffnut is captured, but irritates Grimmel until he lets her go and secretly follows her to the Berkians' new location.

Hiccup and Astrid, who are searching for Toothless, find the Hidden World and see Toothless and the Light Fury leading the dragons there with Toothless now betrothed to her. When the two are soon discovered, Toothless rescues Hiccup and Astrid and returns them to the Berkians, with Hiccup realizing his people would be intruders and unsafe in the Hidden World. Suddenly, Grimmel appears and captures Toothless and the Light Fury (who followed Toothless). Toothless's alpha status allows Grimmel to capture the rest of Berk's dragons by threatening to kill the Light Fury if any dragon or Berkian attacks.

With Astrid's encouragement, Hiccup sets out with the dragon riders to stop Grimmel and his army. Gliding on wingsuits, they catch Grimmel's army off-guard, igniting a battle. Hiccup frees Toothless, while Grimmel drugs the Light Fury into obeying him. Hiccup and Toothless give chase, but Grimmel tranquilizes Toothless midair causing the dragon to fall helplessly. Hiccup, realizing he cannot rescue Toothless alone, frees the Light Fury and implores her to save Toothless. Hiccup is fully prepared to sacrifice himself in order to save Toothless as both he and Grimmel plummet toward the sea. The Light Fury, however, returns to save Hiccup as well while Grimmel impacts the water and drowns.

Role in SAF series.
However, it would not turn out to be so simple, as Grimmel was rescued by His Death Grippers, vowing personal revenge against the boy "That disrupted me", the revenge being strong enough that it earned the attention of a Kingdom Hearts Darkness Slug, a surviving creature from the events of Night of the Night Furies that swam in the Darkness Ooze, and proceeded to attach itself and infect Grimmel, pocessing him and taking full control of him, which in term effected the Death Grippers as well, as the reminant Darkness Slug fuzed forever with the already dark and sinister being, Grimmel internally transforming from an already ruthless man, into what Organization XIII refers to as "Taint Hearts", beings driven by Darkness Slugs to invoke darkness in all living things. Thus, the Darkness Slug had Grimmel return to the humiliated warlords and their armies, turn the trio that were about to scold and turn on him into Heartless, and subugated the surprised armies to his will, as the Darkness Slug took complete hold. Also, to correct a contridiction about claims of him killing off every single Night Fury, Episodes like Drago's Revenge would show that A, he was only a contributing factor when the Night Furies were already suffering deline from a surviveal war with Blackhorrors, and B, reminant flocks actselly both retreated in secluded sactuaries like the Hidden World, giving Grimmel a false sense of superiority in thinking he actselly wiped out an entire spieces said to be extremely smart. Reguardless, he does hold at least some respondsabiliy for their over all absince, ergo, he would be the biggest thorn to the side of peace between Dragons and Humans in the HTTYD World. And now, he is made worse.