NOTE: This Walkthrough will cover, each and every Heart Piece, Item, Boss, and everything else.
Before falling down and fight your last battle against Ganon, I recomend going back to the Light World and use your flute to get to the potion shop. Buy four Blue Potions in case you need them during your battle with Ganon. Also make your you have a bunch of Silver Arrows. Once you are finally ready, fall down the hole at the top of the Pyramid to fight ganon.
Once you fall Ganon will begin to talk to you about how he never thought you could be such a problem to him or that you can defeat Agahnim.
He will begin the battle by throwing his trident from one side of the room to the other while teleporting to the other side to catch it. Whlie he is doing this just strike him with your golden sword a bunch of times.
After a bunch of hits, he will start to wave his trident in the air and creat a circle of firebats that he will send out to attack Link. These are pretty hard to avoid you will get hit a couple times. Continue to strike him with your golden sword when you get the chance.
After a couple more hits with the Golden sword, he will start to use another attack. This one he will create a spiral circle of fire led by a firebat. It will spiral outwards moving in large circular shapes and is pretty hard to avoid. Do your best to not get hit that much and strike Ganon with your sword.
After a couple more strikes, he will start to jump and opund on the ground. Each time he does so a border of the room will fall off starting with the top, then the right, bottom, and then the left. Try not to fall off the sides and try to avoid getting hit by the balls of fire and the firebat.
Once all four sides have been removed the room will go Dark and Ganon will be invisible. Lite the torches at the bottom with the fire rod and you will be able to see Ganon. Be careful of his new attack where he shoots a straight line of fire at you led by a firebat.
Strike Ganon with your sword once and he will be temporarily stunned in which you can give him a shot with a Silver Arrow.
After a short time period the lights will go out again. Lite them once again with your fire rod and then strike Ganon again and hitting him with a Silver Arrow. Three Silver Arrows will be enough to defeat Ganon. Sometimes it takes four arrows depending on how long it takes you to hit him while he has been stunned.
After those three shots the similar tune of Links victory will play as he holds his Golden Sword up in the air.
An opening will be revealed at the top of the room. Head up to get to the triforce.
You will see the triforce floating in the air as the essence of the triforce speaks to you.
After the essence talks to Link about what Ganon had wished for and how he wanted to conquer both worlds, the essence will say that the triforce is looking for a new owner and Link walks up and grabs the triforce. Grab some popcorn and watch the ending while listening to the beutiful ending theme. If you would like to see all the ending screenshots, click here.