I suppose a spear of Dragonglass is the only way, as regular fire can't harm them, but I bet their blue fire is even more devastating. And the Wall is obviously no protection anymore. Well, we're all screwed, says Westeros!
His big bother Drogon will probably be the one to do it.
shareHow do you kill a dragon wight? As opposed to how to kill a dwagon wong?
shareOne of the other dragons, or a spear or some weapon made of Dragonglass would be the best bets right now, other than killing the Night King of course. Maybe even Wildfire would work.
shareLiving dragons are basically impervious to fire. Would an undead ice dragon burn more easily? I'm sure we'll find out.
shareGood ideas. Valyrian steel is another possibility, with a bunch of such weapons in the game now: Jon Snow's Longclaw, Sam Tarly's Heartsbane, Brienne's Oathkeeper, Jaime's Widow's Wail, and Arya's dagger. But you'd probably need to hit a the right spot with enough force to kill it, maybe like Harry Potter sticking the sword through the roof of the basilisk's mouth. Not something many people would want to try!
Killing the Night King is definitely the preferred endgame.