Do not go near this monster in survival mode. It's undefeatable even in creative mode with all my God Items.
However, there is a way to defeat it, which you can see in my comment below.If you want to give the STD Elder Witch Guards (Warning: very powerful), copy and paste the command below into another command block. Enjoy!
/summon minecraft:witch ~ ~4 ~ {CustomName:"Elder Witch",CustomNameVisible:1,Health:32,Fire:0,Attributes:[{Name:"generic.followRange",Base:30},{Name:"generic.knockbackResistance",Base:0.60f},{Name:"generic.movementSpeed",Base:1.4f}],Invulnerable:0,HandDropChances:[2.13F,2.99F],HandItems:[{id:"minecraft:golden_apple",Damage:1,tag:{display:{Name:"The Apple of Notch"}},Count:1},{id:"minecraft:diamond",Count:1}],ArmorDropChances:[0.55F,0.35F,0.99F,0.99F],ArmorItems:[{id:"minecraft:golden_apple",Damage:1,tag:{display:{Name:"The Apple of Notch"}},Count:1},{id:"minecraft:nether_star",tag:{display:{Name:"The Witches prized jewel"}},Count:1},{id:"minecraft:lingering_potion",tag:{Potion:\"minecraft:strong_healing\"},Count:1},{id:"minecraft:splash_potion",tag:{Potion:\"minecraft:strong_harming\"},Count:1}],ActiveEffects:[{Id:0,Amplifier:0,Duration:2147483647},{Id:1,Amplifier:0,Duration:2147483647},{Id:3,Amplifier:0,Duration:2147483647},{Id:5,Amplifier:0,Duration:2147483647},{Id:6,Amplifier:0,Duration:199980},{Id:8,Amplifier:0,Duration:2147483647},{Id:10,Amplifier:0,Duration:2147483647},{Id:11,Amplifier:0,Duration:2147483647},{Id:12,Amplifier:0,Duration:2147483647},{Id:13,Amplifier:0,Duration:2147483647},{Id:16,Amplifier:0,Duration:2147483647},{Id:21,Amplifier:0,Duration:2147483647},{Id:22,Amplifier:0,Duration:2147483647},{Id:23,Amplifier:0,Duration:2147483647},{Id:24,Amplifier:0,Duration:2147483647},{Id:26,Amplifier:0,Duration:2147483647}]}