You are unable to kill the wither if you use /kill @e[type=WitherBoss] while the wither is invulnerable. It will say "Killed Wither", but will have no effect.
You are unable to kill the wither if you use /kill @e[type=WitherBoss] while the wither is invulnerable. It will say "Killed Wither", but will have no effect.
Confirmed
Minecraft 14w02c, Minecraft 14w06b, Minecraft 14w08a
Minecraft 14w10a
Retrieved
Confirmed in 14w04b.
Dinnerbone has indicated that /kill should work even on invulnerable entities, so this is definitely a bug.