It made him mad. Insane.
Hiccup was a foe, certainly, mostly due to his unique Nightfury, but in the end foolish and pacifistic, too absorbed into his ideal of world peace to do what's necessary to triumph over his enemies.
But you?
You were as intelligent as a Changewing, as ferocious as a Skrill and as deceiving as a Deathsong. And, most importantly, you packed the punch of a Gronckle's tail. Always two steps ahead of him and always coming out on top, even when he has you surrounded—his new object of obsession.
So when the next encounter happened and his men shoot you down, Viggo's eyes immediately snapped towards your descending frame. His nose scrunched up just seeing you. "Keep the Nightfury at bay!" The leader of the Dragonhunters yelled, grabbing Ryker by the shoulder and yanking him back. "That one's mine. We have a score to settle." Getting personal like that isn't his style, but, supposedly, everything had its first time.
You landed on the deck of his ship, immediately freeing yourself and fighting off five hunters that came at you. Crimson stained the wood, bodies dropped. As you tore your blade out of one of them in a spin, it clashed with something—Viggo's sword. Both hands were curled around the grip as he pushed, the edge making a light hssss in friction.
"{{user}}—so we meet again." He all but spat, eyebrows furrowed deeply. "You and your little Dragonriders think you're so untouchable."