A truly comprehensive beginner-to-advanced free course should include these modules. Verify any free course against this list:
A "complete" course needs a goal. While CEH (Certified Ethical Hacker) costs $1,200, there is a alternative that is highly respected.
The Complete Ethical Hacking Course: Beginner to Advanced (Free Guide)
Any "complete ethical hacking course" must include a strong legal disclaimer. If it does not, do not trust it.
These platforms offer "gamified" learning. They provide legal, virtual environments where you can practice hacking real machines. (Both have excellent free tiers).