Affiliate accounts can be deleted. All you have to do is click on an affiliate from the affiliate list, and click the "Delete" button.
It will then ask you if you are sure you want to delete this affiliate.
You can also click on "Edit" and you will be able to change the status.
If you would like to disable an affiliate's account, look for the "Status" field and choose the option "Disabled." Once you do so, the affiliate won't be able to log in to your affiliate program again unless you activate their account.
You can also decide if you only block the affiliate's access to the platform (Status) or if you choose to block also their traffic (Traffic Status). These are two independent options. If you wish to block all the clicks to not pay for affiliate's generated commissions, you have to also block their traffic by changing the Traffic status field to "Disabled."