WordNet sense 1 (any weakening or degeneration (especially through lack of use)):

atrophy

WordNet sense 2 (making light of):

devastating, annihilating

WordNet sense 3 (exhibiting lack of respect; rude and discourteous):

disrespectful

WordNet sense 4 (wreaking or capable of wreaking complete destruction):

annihilative

WordNet sense 5 (causing destruction or much damage):

destructive