74 Votes in Poll
Drago indirectly kills a main protagonist. On screen. That makes him exceed Grimmel in my opinion.
While Drago is worse than Grimmel, he has less resources and at least he tortures his own dragons, by forcing them to fly his airship and the apple scene. So my vote is unknown but I wold Grimmel for the sake of I am just doing it randomly, am just tied.
Drago murdered Hiccup's father which was shown onscreen, but Grimmel destroyed Toothless's entire species, leaving him as the last Night Fury. (This means that Toothless will never be able to interact with or even meet another Night Fury.) While we never see Grimmel doing that crime, there's plenty of evidence for it dating back to the first film where Hiccup was wondering why there wan't very much information about Night Furies in the Dragon Manual. To add to that, Grimmel has less resources than Drago, who wanted to conquer the world, but Grimmel wanted to complete his Night Fury genocide. Drago never committed genocide ad never wanted to. I think Drago is just as personal as Grimmel, but it's just matters of who each villain is more personal to (Drago to Hiccup for killing his father, Grimmel to Toothless for killing the rest of his own kind).
However, there's Grimmel's empty threats, where he threatened to burn down Hiccup's house so he would have his entire tribe leave Berk in search for a new home, and he also threatened Toothless that he'll kill the Light Fury to force him to submit to him. However, these weren't just empty threats. They were also very personal threats. Grimmel threatened Hiccup that is he doesn't surrender Toothless when he's ready, then he will destroy everything he (Hiccup) loves. Then, later on, he threatens Toothless that if he doesn't call off the dragons, he'll kill his own mate. That wasn't anyone else's mate; that was Toothless's.
Seeing as how they both fit the criteria for Pure Evil, this is a tough call for me.
What do you think?