To defeat Gannondorf:
- Reflect the balls of yellow light with your sword against him. Once he is hit, shoot him with a light arrow. Quickly after he is hit with a light arrow, jump across to the platform that he was hovering over and slash him with your sword. Repeat this until he is defeated.
* Stay on the outsides of the room, if you go to the middle, he will stomp you and you will be hurt badly.
SPEEDY STRATEGY: If you have the biggorons sword, USE IT! You can use the spinning slash attack and hold it until he tries to hit you with the yellow ball, unleash it and it will usually hit him the first time. Even if it does not, the biggorons sword is much longer and you don't have to worry about the timing as much.
After you defeat Gannondorf, escape the castle with Zelda avoiding the falling rocks and defeating the necessary enemies.
~GANNON~
After you escape the castle Gannondorf will transform into a huge monster. He will knock your master sword out of reach. Equip the bigorons sword if you have it here, it's a big advantage.
Shoot Gannon with the light arrow in the head and he will be stunned. Go to the back of him and slash him with the bigorons sword if you have it, or use the megaton hammer or one of your other weapons. Repeat this until you are able to receive the masters sword. Once you can use this again, you can either use it or the bigorons sword. Keep repeating the same process until Zelda tells you to deliver the FINAL blow with the MASTERS SWORD. Do it, and Gannon will be defeated.
* There are pillars in the final fight with Gannon, if you need magic power or ammo or health, let Gannon smash them. To do this, stand behind them and he will smash them which will drop magic potions, heart containers, arrows, and more.
Good luck.