Zant

In Twilight Princess, Zant is the one who rules the Twilight. He is the main antagonist of the game and possesses powers beyond Link's comprehension. There are multiple ways of defeating Zant, the first suspected way being the three Fused Shadows. When Zant steals these away from Midna and returns her to the World of Light, the only option left to defeat Zant is to find the Twilight Mirror.

Boss Strategy
Zant is one of the more complicated bosses out of all of them. He will at first move to the Forest temple boss arena and float above the poisonous water and shoot you with balls of dark energy. Block these with your shield and use your Gale Boomerang to knock him down while he tries to get more energy. He will bounce around and land on the ground, attack him with your sword. Repeat this a few times and he will be defeated in this area.

Next he moves to the Fire Temple boss arena and continuously will keep jumping making the platform move down. Avoid falling down by using the Iron Boots when necessary. Eventually he will stop and attempt to attack you again. When he is tired remove the Iron Boots and quickly attack him. Repeat this a few times and he will be defeated in this area as well.

Next he moves to the Lakebed Temple arena. Be sure to equip your Zora armor to breath and your iron boots to float to the ground. There will be multiple helmets like Zant's on the ground. One will open up and inside will be Zant and he will attack you. After he is done he will wait a few seconds before he closes the helmet. At this point quickly use the Clawshot to pull him out and attack him. He will go back into the helmet and you will have to figure out which one he is in and then repeat the process.

Next he goes to the mini-boss arena in the Forest Temple. He will jump around the pillars and first use your Clawshot to stun him, and then role into the pole to knock him down, and attack. Repeat this a few times and again the arena will change.

Next he goes to the Arbiter Ground's arena and you will have to attack him the same way you did with Stallord's head.

After attacking him a few times in Arbiter Ground's he will go to the Snowpeak ruins and jump around the area in a giant form. Hit him in the feet with the Ball and Chain to make him shrink down into a size that you can attack him with the sword. Repeat this a few times to go to the next area.

The final arena is just outside of Hyrule Castle. He will simply attack you with two swords he has and you have to avoid them. Occasinally he will do a spin attack and be left dazed for a few seconds. This is the best time to attack. After a bunch of hits Zant will be finally defeated.