Having trouble with all of those nasty bosses in Final Fantasy XIII? Don't worry! We've got you covered on all the hardest bosses in the game!
Make sure that Lightning is carrying an upgraded spark ring and that Hope has the fully upgraded silver ring. The fight is much easier if Hope stays alive.
Paradigms should be MED/SYN. Use lots of cures and potions whenever you can, Odin hits hard and fast. Hope should be casting protect and shell, which will help you stay alive. If both characters are fully buffed, then switch to RAV/RAV or RAV/MED to attack.
If you want extra security, use an aerisol before the fight so that you are already buffed at the start of the battle. Don't forget to use Libra so that you know what spells to attack with!
You will be healing a lot in this fight, but it is necessary to win. This boss is hard to stagger, so don't worry about it too much and focus on staying alive. Equip the doctor's code accessory so that potions can heal both characters for 300 each, this is more effective than using cure.
Start with COM/SYN and switch to COM/RAV or RAV/RAV after Hope buffs the both of you. Be sure to use Libra and summon Odin when he staggers for big damage. Switch back to COM/SYN when your buff wears out and repeat the process. After summoning Odin, you can hit the square button to go into gestalt mode and hit buttons for some extra damage.
Just like with Aster, it is probably better to buy a lot of potions and use the Doctor's code accessory so that you don't have to switch to MED too often. It is probably best to bring in Fang and/or Vanille with you since Fang can use Slow and Curse while Vanille can do DeProtect and DeShell. Of course, bring someone who can cast Shell, Haste, Bravery and Faith to buff your team.
First, destroy the four targets around Barthandelus. Use Libra because they all have different weaknesses. Attack with RAV/RAV/COM. Once the four are gone, debuff Barthandelus and attack/heal as in a normal fight. However, once he starts to use Destructo, switch to RAV/RAV/COM and hit him with everything you've got! You basically want to make him flinch. Once that happens, heal up because he will still finish the attack, but at least it is a weaker attack now.
This boss uses a lot of buffs and debuffs. You should probably use fortisol and aegisol before the start of the fight so that you can focus on debuffing him right off the bat. Use Slow and other status debuffs. Start off offensive and try to get his stagger bar up. It will take a while, so be sure to stay healed up. Again, Doctor's Code is a good idea.
If he goes into guard mode, don't bother attacking and just focus on healing, buffing, and debuffing. Once you take away half his life, he will transform and start hitting harder and using even more buffs. Don't be afraid to switch to MED/SEN/MED in an emergency, especially after he removes all your status protection.
You might want to level up your party a bit before this fight. Bring two good medics with you and start the battle with haste and slow. A sentinel character is good too for absorbing damage. Be sure to equip your team with accessories that will help you resist against status effects, especially daze. If you have a rainbow anklet, give it to your medic, who can then use esuna on your team when needed.
Keep your health up throughout the fight, as Barthandelus can hit your whole team for a lot of damage with one attack. Also keep your buffs and debuffs up to make the fight easier. He is easy to stagger, so time the moment right so that you are fully healed and can attack all out once you stagger him.
This boss is hard to stagger, you will most likely just have to attack him to death the normal way. Bring a good sentinel and someone who can do commando and medic well. Don't bother with buffs or debuffs for this fight, they won't last too long. Physical attacks is the way to go here.
Focus on keeping the sentinel alive. Buff him with protect and switch to medic whenever you need to. There is no real strategy, the rest is just a survival game here.
Be sure to equip items with instant death resistance, like the fully upgraded Cherub's Crown here, you'll need it. In the first form, Barthandelus will stagger very easily. When that happens, hit him with Lightning's Army of One to get your chain bonus up to reach max damage faster.
Make sure to use as many buffs and debuffs as possible. You will definitely need to bring someone who knows DeProtect, Deshell and slow. The boss' attacks will hurt a lot even with Shell, so stay buffed up and healed.
When you start to fight the second part of the battle against Orphan, you will get knocked down to critical levels right off the bat. Heal right away and watch out for poison, because if that attack comes out again, you might lose a character before you can heal them.
You should try poisoning him as well and be ready to go all out once he staggers. The rest is just surviving and slowly building up the stagger bar again. Buff yourself and debuff him as much as possible. With a bit of luck, you'll move on to face Orphan's second form.
Orphan's second form will take no damage until he staggers, so build up that bar! Make sure you're well healed before you stagger him so that you can let him have it without worries. He doesn't have too much health, so try to finish him off on the first try by keeping him in the air for as long as possible.