Dragons in equestria are truly a terrifying creature.Other than comedic effect, we've never seen any of them be injured by anything less than attacks from another dragon. The gauntlet of fire was nothing more than an obstacle course and other than the possibility of Ember drowning, none of the dangers were actually dangerous to the dragons. Volcanic explosions? The wimps turned around. Massive shards of ruby slamming into them? The wall gave way before the dragon did and he was up and ready to fight two other dragons in no time.Look at all the abuse Spike has suffered and document one case where he had an injury that lasted for more than one cutaway; it's impossible since he doesn't get injured.The closest we can see is when Spikezilla's head spines were cut off by the wonderbolts, though those scales seem to be as flexible as hair.Honestly, had he n0t loved Rarity as much as he does, Spikezilla may have been one of the most dangerous events to happen to ponyville due to how indestructible dragons are in this series.