Reeking Douglass, level 105 - Most people agree that Douglass is the easiest superboss. It neither attacks too quickly nor hits too hard, and its stats are relatively low. Its gimmick, however, is that it can summon reinforcements. That said, combos ending in Darkness can Seal Reinforcements, making this one easy to cheese.
Pernicious Benf, level 109 - Fans of the original Xenoblade know what a pain in the *** behemoths can be. Benf has some high stats all around, with its high HP taking some time to whittle through, and its high damage attacks can hit the entire party.
Cloud Sea King Ken, Level 110 - Ken is probably responsible for scaring the most people because once Chapter 10 rolls around it pops up right in the middle of Tantal's lower level during fog. Despite this though, it's actually not too hard IMO... Its attacks are the same as a generic Squid, but just more powerful due to higher stats. That said, Tentacle Storm can be a major issue since it hits your entire party, and will inflict knockback repeatedly. But the aforementioned specials' animations can absolutely drown it out.
Mk VII Arek, Level 114 - This thing is notable for having really low HP, but this is offset by the fact that it summons reinforcements. And it does so much, much more than Reeking Douglass does... it summons the Sovereign type mechs, which in turn are capable of summoning their own reinforcements since they can launch the Bike type mechs. The reinforcements are what make this fight annoying since you can get overwhelmed if too many spawn... But the same Seal Reinforcements works, and the boss itself has low HP, so it'll usually die to a 3-orb chain attack at most.
Artifice Ophion, level 117 - The biggest spoiler superboss. Ophion IMO was the hardest one if only because of how the battle is set up. He flies over a bottomless abyss while you fight him from the cliff; this means that all potions will drop directly into the abyss, and positional arts are almost out of the question (you can get a little bit of the side but back is impossible). Unlike most enemies, it does not autoattack. Instead, it just spams Arts. This means its damage is higher, but it also attacks more slowly with breaks between arts. This is the one boss that you absolutely want to make sure you time your level 4 specials and 3rd tier combo specials well to avoid his attacks, because with how slow they are you can block out a lot of damage that way. Also, watch out for this barrier field; when it goes up, stop attacking because that Reflect will kill you.
Chickenheart Dagmara, Level 120 - Without a doubt the most annoying superboss in the game. It has pitifully low HP, so much so that a 2-orb chain attack can easily overkill it. The problem however is that its Agility is stupidly high so a lot of attacks will miss, and it loves to spam an art that gives it perfect evasion for a few seconds... this boss battle is made much more difficult because of attacks frequently missing. It also doesn't help that it can topple you frequently. Still, when attacks do land they'll make its HP bar drop.
Tyrannotitan Kurodil, Level 130 - The highest level enemy in the game, but not necessarily the hardest. It's a major tank and spank, but he does have a few gimmicks, the most notable of which is an art that can one-shot a Driver with a few seconds of delay. Other than that though its attacks are manageable, although the AI will die if they stand behind it, as its tail can deal high damage and knock them back (Nia found this out the hard way for me).
