The Kraken is a harder boss to deal with.
Lvl: 24
HP: 8000
Atk: 55
Def: 27
Weakness: Lightning
A black mage with Thundara is very useful here as well as having some Zeus' wrath. This boss packs a lot more punch than the previous ones. I personally accomplished this with 3 dual wielding freelancers and a black mage however I did suffer a casualty(Ingus). I actually had to fight him twice because I didnt save later on and lost a lot of progress because I got stupid and died, and Ingus died both times....
A mage with Thundara should do 1k of damage per round. If you could manage a second, you are golden. Luneth was my stongest freelancer and was doing about 600 damage, Arc would hit for 400-500 and Ingus was pretty weak tbh so he was dishing out the Zeus' Wrath for another 1k worth of damage(approx). You should be able to dispatch him in 2-3 rounds.