seems the unbreakable tag for wolf armor makes the wolf impossible to be killed. here its wolf spawn egg with wolf armor with unbreakable tag on the wolf armor:
/give @p wolf_spawn_egg[entity_data={id:"minecraft:wolf",body_armor_item:{id:"minecraft:wolf_armor",count:1,components:{"minecraft:unbreakable":{}}}}] 1
wolf can be hurt but don't die even when in lava or fall from high ground. think this its bug.
Comments 2
Thank you for your report!
After consideration, the issue is being closed as Working as Intended.
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have you tried /kill?