Actually, my friend discovered this bug, so we cooperated with one another. He sent the videos to me and decided to report this. So here is how it goes, one day my friend played creative mode in Minecraft. He experimented to fight the drowned and the snow golem. The snow golem died, but it keeps reviving and throwing snowballs. Later that, he experimented with the snow golem on land. He decided to blow it with TNT. But it didn't die. He experimented again until he discovered that it can be killed only with a splash potion of harming.