Hi,
My Query,
I have two Gallery List with Names, Gallery A Consist of all the Names, and Gallery B has to be compared with Gallery A Names and List the names which are not present in Gallery A.
Thank You.

Hi,
My Query,
I have two Gallery List with Names, Gallery A Consist of all the Names, and Gallery B has to be compared with Gallery A Names and List the names which are not present in Gallery A.
Thank You.
Try adding the below to the Items property of your third Gallery to get the differences:
Filter(Gallery2.AllItems, Not(Title in Gallery1.AllItems.Title))