Summon Board Passive selections:
Odin choose 3 / 6 / 7
Bahamut choose 4 / 5 / 6
Ifrit, Shiva, Ramuh, Brothers 4 / 5 / 7
Leviathan, Pandemonium, Diabolos, Alexander 4 / 5 / 6
For more details and help with summons, check Summon Hub!
A Spheres - 100% focus on ATK, Melee ATK, or BRV DMG. Nothing else matters. If you get an ATK/mBRV combination, that’s a convenient bonus since he holds onto a good amount of BRV due to his BRV gain absorb, constant BRV refund, & sap debuff.
E Sphere - Here’s where things get interesting. You have 2 choices, give Kadaj an ATK sphere since he’s a damage dealer, OR exploit his Stigma debuff and get some marginal utility out of an otherwise garbage sphere.
Ultimecia’s sphere (or RF) is the best sphere for him. He can reliably trigger it to inflict 6T of 30% (12% for RF) DEF down on an enemy. Now usually, 30% on a generic debuff is a waste of a debuff slot but because of Kadaj’s Stigma debuff, this 30% DEF down will be framed and gold, so it cannot be removed. Because it is technically still considered a generic debuff, you can use another ally or call to inflict a better DEF down debuff, and their better DEF down debuff will replace Kadaj’s and be gold framed and irremovable!
Faris call works well with this setup, but note that you want to get your other important debuffs like Kurasame, Raijin, Seymour, etc BEFORE using Faris call. Faris call + Kadaj = 7 debuffs, so expect to have no room left after you use her call!
If you still want to use a debuffing sphere, and no Ultimecia sphere is in hand, Laguna/Fran for mBRV is the next best, and you can use Kadaj on the same team as Serah for a 60% framed mBRV down.
As mentioned above, he wants melee allies to get the full 80% per turn (100% on echo)
Cor and Weiss are his best buddies with their general plug & play strength and extra damage. Even if they're not boosting Kadaj's BT phase, they + Kadaj will heavily enhance any attacker with their linked attacks.
Leo and Noctis are also great allies especially in single target fights as their follow ups are purely single target and Leo needs to have a specific enemy attacked (his specific debuff).
We recently got Papalymo who LOVES taking turns for himself. Well he also loves Link attackers and Kadaj is great for that role.
For single target focused fights, consider Crystal Passive U6 for some extremely high damage in Force Time/Retain.
Removable PassivesNOTE: Passives should generally only be removed if you lack CP space. There are very rare occasions where a character has a bad passive that disrupts their optimal gameplay.
BRV Attack++ HP Attack++ Up (you will never need to use either of these, and even if you do, you won’t need this passive’s effects anyway)
Buff Speed Up (10% SPD) - marginal effect with no other stats associated, but note that it may be hard to upkeep his debuffs if you slow him down!