The best way to do this is to add Conditions on this specific task on the workflow, or create a business rule if you want any task that is Closed Incomplete/cancelled to cancel the RITM. When an RITM is Closed Incomplete, there are out of the box Business Rules in place to close incomplete any other open tasks and cancel the workflow. To add Conditions, right-click on the task activity, and choose Add Condition. You should have one condition for each inactive catalog task state, so out of the box that's Closed Complete (3), Closed Incomplete (4), and Closed Skipped (7). Give the condition a Name, then in the Condition field type activity.result==3 for Closed Complete.
Repeat to add the other conditions, then right-click directly on the Always condition and choose Delete. Now all you have to do is route the paths accordingly - you may want to continue on to the next task/activity if Closed Complete, and maybe Closed Skipped too, and point to an activity that makes the RITM Closed Incomplete if the task is Closed Incomplete.
In this example the Set Values activity is setting the (RITM) State = Closed Incomplete, Active = false, and the Stage to Complete.
