Swamp Nitwit Villager with infinite health by porcusheep

Literally unkillable even with the /kill command so use with care....

If you choose not to ignore my warning above, and need to kill him, the only possible way is to use the following command within 5 blocks of him:

 /minecraft:data merge entity @e[name=Nitwit,distance=..5,limit=1] {AbsorbtionAmount:0}

Then you can kill him like normal.