1. Go to Administration > Global Changes.
2. Click Add > Delete constituent attribute.
3. Click OK.
4. Name the process.
5. Choose a selection or leave it blank for all records. 
6. Choose the Attribute Category that you would like to delete.
7. Click Save. 
8. Highlight the process and click 'Start Process'.

This will remove the attribute from all records with the attribute. 

To delete the attribute entirely from the database:

1. Go to Administration > Attribute Categories. 
2. Highlight the Attribute and click 'Delete'.