If you are not familiar with the basics of automation, you can check them out here.
Make sure you have a drip sequence ready. If you need help with that, click here.
Create a new automaitons by going to the Automations > Create Automation from the main menu.
Set a name for automation.
Under Trigger, make sure you have SendX selected in the field on the left-hand side. On the right-hand side field, choose Removed from a list.
Choose the name of the list associated with this particular drip, which you want to use as a trigger to stop the drip.
Under Actions, keep SendX as it is on the left field and select Removed from a drip from the dropdown. Select the name of the drip you want to unsubscribe from.
Click Submit Automation to save this automation.
And that's it! That's all you need to do to stop a drip sequence on a user unsubscribing from a list in SendX.