The Hobbit movies had Galadriel defeat Sauron in Dol Guldur by hulking out and using Nenya (making her resemble her 'beautiful and terrible' Ring-bearing queen form), which is fucking ridiculous. Sauron is a Maia, or angel (albeit fallen) in Tolkien's cosmology, like Gandalf or Saruman or the Balrog, and Maiar are well above any Elf in power. IIRC it was Saruman & Elrond who fought the Ringwraiths in that particular scene, while Galadriel was focused on protecting Gandalf from Sauron.

While First Age Elves did fight Balrogs, only one was able to win - Glorfindel, who killed the Balrog chieftain Gothmog at the cost of his own life; and Gothmog in turn had previously killed Fëanor, canonically the greatest and mightiest Elf ever, although he needed the help of a small army of his fellows to do it. Sauron, of course, is mightier than the Balrogs (which was why he was Morgoth's #2 guy and not Gothmog) and even in his maimed Ringless form would've been more than a match for Saruman (hence why he just gave up and joined Sauron later) & Gandalf (at least as 'the Grey'), much less Galadriel.