Ancient red dragon. AC 22. HP 546. Peasant with a longbow has a +0 to-hit, so needs a natural 20, which crits and deals double damage. Using the average, doubled, is 9 damage. For every 20 peasants one will hit and deal 9 damage. So it would take 61 hits to kill the dragon which would take 1220 shots to accomplish. Which means one round of attacks from 1220 peasants, two rounds of attacks from 660 peasants, three rounds of attacks from 440 peasants, etc. According to the DMG, a village is up to 1000 people. So yeah, a village of armed peasants can literally shoot an ancient red dragon out of the sky in about two rounds. That matches everyone’s fantasy, right?