Title, pretty much, With /godmode on, you theoretically should be supposed to not take any damage from any kind of entity. The aggressive trait of, say, the Sinister Queen deals pure damage to the player, even with godmode on. Silly, I can swim in lava, but a bee can kill me. Even gods bleed, I guess.
There are quite a few different mods that adds custom ways of killing, which bypass the /god. Most modders are aware of the various /god commands added by plugins, but either don't care about it, or they create a way of dying solely to bypass it (They dont want a cheaty/easy way)