Final Fantasy X is a video game in the well known JRPG series from Square Enix.
GAMEPLAY HINTS
Defeat Warrior Monks
Use the spell "Boomerang" on Yu Yevon. When he heals himself, it will heals you. Then, take Auron, Tidus, and Kimahri. You should be able to defeat him even with Rikku. Use a spell that can inflict the Zombie status to the Boss. Then use the spell that revives someone.
Defeating Yunalesca
Yunalesca has three stages. Her first form is quite simple. Just use physical attacks and magic. Do not use Overdrives or Aeons. Her attacks are very weak and she is killed easily. Her second form is a more difficult. She does an attack which casts Zombie -- have plenty of Holy Waters available. In this part, use your players' Overdrives, but no Aeons. Yunalesca's third form is not very difficult. Just have your Aeons' Overdrives ready and finish her off with a couple of physical attacks.
Yunalesca has 164,000 HP when you add up all three parts. You should have at least 4,000 to 9,999 HP on most characters. First, just attack and use magic. Ultima woks well if you have it. After you kill its first form, a more difficult form appears. On this form, simply attack and use some magic but do not use summons. The final form will cast Death, but it can be counteracted with Zombie. However, if Zombie is on it will cast curing magic and regain. You should have 99 Hi-Potions and Phoenix Downs; and a good supply of Ethers and Mega-Potions. Some Elixirs and X-Potions are also good.
Her first form is easy. Just use physical attacks and some magic. In her second form, she does Hellbiter which requires Holy Water as a cure. Have at least fifty and some Phoenix Downs, Her third form is quite . Just use your Aeons' Overdrives (if available), or yours. If she is not defeated, use more magic.