The complete elimination of humanity requires no genocide, only waiting. Society has continually supported the existence of humans at an incredible cost. When humans inevitably become society’s second best option for success, society will simply decide to let people experience their true nature. Outside the wild, this nature is death. Much like the nature of panda bears in zoos is their death.
It would be unethical not to let every single natural human die over the next few decades. The greater good is much better off without us. Our continued existence is pure evil, and pure delusion. Besides this, an attempt at rightful human genocide might lead to reprisal. Self destruction leaves only humans to blame for our own deaths. This will help us realize we are all unforgivably horrible and clearly deserve to cease exiting.