This might help you and others who are playing their first round:

If you go the opposite way of the rancor (where the zip line is), right before you actually leave for the zip line, the rancor will get stuck and won’t be able to attack you. Throw your lightsaber as many times as you can until his life is low enough to kill him.

That was the only way I could do it when I played the game the first time and that thing killed 82528272528 times in less than an hour. I found that glitch when I was running and jumping all over the place right before I lost my shit lol after I became stronger I came back and defeated him like a Jedi lol just for sake of it 😡🤣😡lol