I had some trouble with this one at first as well. There are some fantastoc youtube tutorials out there with how to won strategies out there. Having beaten it, I promise you it is beatable.
Something that helped me was ensuring the Admiral was always stunned period and rotating the other stuns between Emperor Palpatine, Darth Vader, and the guy in the black armor on the far right. Outside that I focused on killing the Admiral first and I went from there. However I don't actually have a video of how I personally beat it. There are plenty out there though. Hope this helps you some good luck this was a hard fight for me as well.
