In case you need to delete a SharePoint site (and its entire content), the process is pretty straight forward.
The same applies for SharePoint 2013/2016 and SharePoint Online (at the time of writing: Dec. 2017)
Assuming you have the correct permissions to do so, simply follow these steps:
- Log into the SharePoint site you wish to delete
- On the top left corner, click on the gear icon >> Site settings
- Under Site Actions, click on Delete this site
- Make sure you read and understand the implications of deleting the site
- Once you’re sure, click Delete
- Then click OK to send this website to the Site Collection Recycle bin
If you have any subsites under the site you are trying to delete, the deletion will not work. You need to delete the subsites first.