In the end finally, Link fights with Ganon in two forms. First is in the castle and second outside when Ganon is his true form.
Main Quest: Destroy Ganon
In this main quest Link goes to the castle and finally deals with Ganon. In the first stage, you have to deal with Calamity Ganon. Half of his health will be destroyed by the attack from Divine Beasts. You will need to skip his attack and you can use the bow and arrows as the best weapon to take him down. It will be a long process, also you get power from the beast to use at the devil.
Finally, after taking him down, you have to next face Dark Beast Ganon. You will use Bow of Light for this beast. There are certain glowing points that you have to target to take him down. It will take a pretty long time. And this will be done over the horse.
The best way is to run sideways and attack the points on the back or side. The beast takes a good amount of time to turn around. you can then pass his attacks and move on the other side for attack. The glowing area will be appearing on the side, over the front and back legs. A final one will appear on the head at the end. It has enough amount of health, but the good thing is that the best is very slow in attack. So you can run a distance and shoot it. Stay as far as possible to dodge its attack also. Finally in the end when it dies the final cut scene shows the princess.
This was the end of Legend of Zelda: Breath of Wild Walkthrough Part 8. The final cut scene in the end reveals the princess took a final attack to end Ganon. You can also refer to our Legend of Zelda: Breath of Wild Wiki Guide for more tips and tricks.