which technique is unethical and can be reason for banning?

[WoodsPainting]

which technique is unethical and can be a reason for banning?

[ImpalaWardrobes]

Black hat tactic is unethical and reason for banning.

Content Automation
Doorway Pages
Hidden Text or Links
Keyword Stuffing
Reporting a Competitor
Sneaky Redirects
Cloaking etc

[PrimeItSolution]

Creating a doorway page instead a home page is considered as unethical because doorway pages are aimed at misleading search engines.