Hi ‌

You will see the person who actioned the task in the workflow history.

You can also get this person by using the Common Reference of Last Task Respondent (user login) or the Last Task Respondent Display Name.

Hope this helps

‌ ‌ ‌ ‌

Refer following posts :

How to know who approved or rejected a request approval task

Nintex – Get approver name when task assigned to a SharePoint group | Learn with Shreedevi... 

Thanks , but I found the "Last Task Respondent" only to work if you enable the option to "Create individual tasks for all group members".

In some cases this is not ideal in that it creates a bunch of Workflow tasks that end up being "Not Required". So the alternative is to extract the Approver name from the Approver Comments using a regular expression, as linked by ‌.

Hi ‌

Sorry, I nearly always have that option checked as I don't have SharePoint groups with that large membership, I also create new task lists for each workflow to avoid performance issues and to make housekeeping easier. The link provided by ‌ is the way to go.