This is a pretty malicious keylogger I wrote just to learn Windows automation with Python. I wouldn't recommend using it on anyone but it's your life tbh. It runs as a silent background process and you can't shut it down unless you go through Task Manager so you're pretty much going to go undetected.
You'll have to install it on to your victim's device.
Download the zip/clone the repo and run
pip install -r requirements.txt (remember to download eveything in the repo).
Then just figure out how to get it on to your victim's computer and edit line 3 of
log.pyw to point to a .txt file that your victim won't easily discover.
Disclaimer: I do not condone the malicious use of this software.