@kirti are you writing your Report definition on work class? Can you please send the screenshot of your RD? Seems like you are showing original user and current user for all the cases. If my assumptions are right, you can use sub report on Assign-worklist to get the name. Pass pyuseridentifier(your pxflow()…) To sub report and use that as filter on sub report and fetch the operator name and use that in main RD column.
@kirti ok. kirti, the first operator to which assignment got routed is the orginator. But if you run report initially, originator will not displayed. For that what you need to do is set originator in pre flow action of first assignment. Because currently you are setting originator on reassigning. You need to maintain a flag. So once it is reassigned, originator property should not be set again.