Here is how you get rid of your Twitter account permanently

1. Log in to Twitter via your web browser. 
2. Click on your profile picture in the upper right corner to access the menu.
3. In the menu, choose Settings and integrity
4. Click Inactive your account which is at the bottom of the page.
5. Confirm

If you choose to delete your Twitter account, all of your user data will be deleted after 30 days. If you regret doing this within those 30 days, you can reactivate your account through logging in with your username and password.