You can end an Automation in 2 ways:
Pause an Automation
Delete an Automation
To pause an Automation:
Click on the Automations tab
Click on the 3 dots to the right of an Automation
Select Pause
To delete an Automation:
Click on the Automations tab
Click on the 3 dots to the right of an Automation
Select Delete
OR
Click on the Automations tab
Click on an Automation
Click on the trash can icon