I think it's stoick...but if its valka...I will never forgive him....maybe it's cloudjumper...I'm just so sad now

cause as much as I like him, it's not that much important

Now, who is Toothless likely to kill? It's not going to be Drago, unless the reviewer has a very odd definition of "supporting character." It's also unlikely given that the review implies that there's quite a bit of action after this bit, though I suppose a rampaging Bewilderbeast or two could provide more than enough action.

Cloudjumper is a possibility, since the evidence suggests that he/she does die. This would even be quite probable if it happens during the bit where Drago controls Toothless. I suppose it would be a bit of a cop-out then, since it would serve as an instant excuse for Toothless' actions that would completely remove the interesting moral ambiguity that could result from this situation.

If we're going down the mind control route, then basically anyone is a possibility, depending on how one defines "supporting character." My gut would say Stoick is the most probable candidate, simply because it will pack some emotional punch and because he's almost certain to die at some point, either in this film or the next.

If we're not bringing the mind control into this, then there are very few candidates that would make any sense. Eret's technically a possibility, but I think it's all but certain that he'll join the good guys at some point. My gut says one of the Bewilderbeasts would be the most likely candidate in this scenario, though how the heck he would pull that off when they're ice dragons (and thus not handily combustible) is beyond me. It would, however, be awesome, assuming it made the slightest lick of sense.

Of course, most of you can probably figure out who I want him to kill, but there's no way my hopes are jumping up that high in one day. Besides, if Valka Villain Probability was actually to take effect, some reviewer would probably have hinted at it by now. Probably the same one who gave this information.