In the episodes of Shell Shocked, Ruffnut and Tuffnut mention how Viggo would actually be fun to hang with if he didn't try to kill them all the time. Can you imagine Viggo being among the chaos of the Edge? I'm telling you, he wouldn't last a week.
Hiccup: *jumps off a cliff*
Viggo: Fishlegs, are you alright?
Fishlegs: I will only tell you this once, senile old man, the name is Bonecrusher, Thor Bonecrusher
Viggo: should you not be at practice?
Snotlout: no, I quit the dragon riders. I will now be a beggar in the streets, all alone, cold, like my dead heart.
Tuffnut: I kissed a frog :D
Viggo: finally, a sane person
Astrid, carrying two axes, five knives, a spear and a sword: kill
Viggo: understandable, have a great day
Ruffnut: *sitting behind a game board*
Viggo: ah! Maces and Talons, may I join?
Ruffnut: can't. I ate the pieces
Ruffnut: I ate the pieces
Ruffnut: don't tell Hiccup
Ironically, Viggo finds dragons are the most sane creatures on the island.