Page Layout - task related list

You could change in the page layout for Leads, Accounts, Contacts and cases the related list Activity History and add the field call result. This will give the user the result of the call while checking the task list.

in the Activity History list, add the field: Call Result

The user will see the result in the activity history list

Create a new compact layout for tasks.

Add the field Call Result

The user will see the result in the activity history list