How can we Unlock the BOSS NEMESIS at the Arena (Calm Lands)?
And also what suggested characteristics the combat team should have and what formation?
According to this article,
you have to capture 10 of EVERY fiend in the entire game... then you have to beat all of the Area Conquest, Species Conquest and Original monsters in the arena.
Also provided are preparation tactics:
you MUST have weapons that have Break Damage Limit and One MP Cost, armor with Auto- Phoenix and Auto-Haste would be nice too. Have the person/people with One MP Cost know Auto Life so the others do not have to waste precious MP casting it. Quick Attack is also helpful.
Nemesis is the final boss of the Arena post-game and arguably the hardest boss in the game with the exception of Penance. It is unlocked by capturing 10 of every fiend then beating every area, species, and original creation at least once.
Unlocking Nemesis rewards 99 Dark Matter, which is enough to customise Ribbon onto an armor.
The ideal party includes Rikku and Wakka. Rikku's Mix- specifically Hyper Mighty G- is the strongest support ability in the game. Wakka's Overdrive Attack Reels deals the most damage (1,199,988 with perfect, celestial, and Strength).
The best third character for the post game is Tidus but it matters less. Swapping him for Yuna is fine if you can't beat the chocobo minigame.
All characters should have their celestial weapons as they ignore nemesis' defence stat. Statwise, 255 strength and 170 agility (the cap) are strongly recommended. Luck is not necessary to hit here. Magic is pointless in most cases. Other stats depend on your strategy- what attacks do you plan on surviving? Nemesis has the following moves:
If you are playing without break hp limit, you need Auto-Haste and Auto-Phoenix. There are options for the other 2 slots- you don't need stoneproof or ribbon here but it depends on how many sets of armour you have the patience to farm for. The standard endgame Auto-Protect + Ribbon/Stoneproof is fine though Auto-Potion is also an option.
If you are playing with break hp limit, you will have 99999 hp and maxed defenses. The armor in that case will be Auto-Haste, Ribbon (if you farm 99999 hp, you can farm 2 ribbon armours), and Auto-Regen.
The fight itself revolves around mixing Hyper Mighty G or casting auto-life at any point where the boss might use Ultra Spark (if not breaking HP limit) or Armageddon.