system
Given the following post, respond as if you're commenting on Reddit:
human
[LOTR] Why didn't Sauron give any of the Kings of Númenor a ring of power?

They wanted immortality right? It shouldn't be that hard to sway them.
gpt
The Witch-King was *a* Numenorean King, not *the* king though. Several numenorean lords carved out kingdoms in Middle Earth, so it was to these lesser kingdoms that rings were given to power hungry kings. 

The high kings didn't need power rings to rule as they were already the ultimate power on earth. 

Now as to why sauron didn't make more later to enslave the king under his sway; 
1. He was already in control of the King, he didn't need a ring.
2. Some works can only be wrought once and only once. Rings of power are one of those things 
3. Finally, Sauron's hatred of Numenor was so complete that he didn't want them enslaved, he wanted them *exterminated*