Question What is the minimum WATT needed for 9900K cpu without graphics card?

Not sure and did not check, but............

Intel's TDP rating is 95 watts.

It's not easy to find a high quality PSU of under 550 watts.

I'd certainly think that 550 would be plenty unless you have some extreme situation.
More than enough for the CPU only.

Whether the power supply is junk is another question.

But watts alone? Sure, that's enough.

Drives, monitors, RAM, motherboard all take additional power.

System total could easily be under 200 watts maximum.

I wouldn't have any qualms about a 9900K with a good 450 watt PSU on an ordinary system that had no graphics card.

Will you connect 4 monitors or 8 hard drives or anything wild like that?

Will you have all of the slots full on the motherboard....other than graphics?