Minecraft wiki entry for Defeating_a_bastion_remnant, associated text: Piglin brutes are not immune to fire damage, which makes lava buckets a very efficient way to kill them. Simply use the lava bucket on the block underneath the piglin brute to make them receive high amounts of damage without aggravating other piglins. However, remember that lava flows faster and further in the Nether, so a single lava source could potentially kill lots of piglins or make exploring the bastion harder. This is why you might want to quickly refill your bucket and place the lava again over and over until the brute dies.