If Jaime Lannister was panicking about three living dragons, everyone in Westeros should be panicking about this one evil dragon. When Bronn shot Drogon in the shoulder with Qyburn's ballista, The Scorpion, the dragon came down, but it didn’t take the beast long to heal -- if anything, it was more like a shoulder cramp for the poor thing. That’s the best weapon humanity has against dragons and it doesn’t even work on a dragon that still has blood pumping through its veins. The Scorpion would have to have giant dragonglass spears to down White Viserion, or a Valyrian tip. Presumably Viserion is still as resistant to piercing damage as his living brothers, making spears, arrows, and swords moot.
Here’s some food for thought: if White Walkers can change any dead thing (be it human, giant, or polar bears) into a wight could Viserion transform large groups of the dead just by landing near them? That would be… bad.