There are several potent combinations, but Stillness (neither the player or the enemy takes any damage for 2 turns) from the Spiritmaster class is probably the worst offender. Coupled with the right setup (e.g. Hasten World ability, or My Hero from a performer) it can make the party impervious from any kind of damage; the only real thing to watch out for are status effects, and those can be countered with the right accessory/armor, or just have the Spiritmaster cast Fairy Ward. The way it works is all you need is for the Spiritmaster to go before the enemy, and for at least one party member to go before they do. That means that your faster party member attacks, then Stillness stops damage output entirely for 2 turns, meaning the enemy NEVER gets to deal damage.
If you use the demo exploit to get 20 villagers on your file, you can easily get your hands on both the blessed shield and the MP recovery special move parts before you even awaken the first crystal. By having your healer brave-spam cura using the blessed shield at the start of every random encounter, your entire party will regain MP every three random battles because you'll keep reactivating your staff special with the aforementioned MP bonus parts. Combined with at least two dedicated physical fighters, sometimes even just one, it will be a very long time before you have to worry about pacing your magic use in a dungeon again. And if both of your physical fighters happen to have hidden dragon so that they're guaranteed to attack after your healer spams cura from the shield, and you can still breeze through random encounters in one turn without risking your healer not getting to go.
Although there's a random element to it you can get guests via the on-line functionality who are orders of magnitude stronger than your party. Using summon ally to get them to help you can make defeating early bosses absolutely trivial as they'll one shot them.
Freelancer/Performer: My Hero followed by three Mimic, giving your whole party 4 BP one turn out of two (unless you carry Hasten World or put low leverage into effect, in which case it's available every turn), and since it costs nothing else than BP, can be used indefinitely.
Red Mage/Black Mage: Group-Cast All with BP Recovery equipped on everyone gives similar results to above: you can cast a status effect such as Poison on your entire party up to 3 times and gain up to 6 BP out of it and spend the remaining turn to cure it right away with Esuna or Poisona before it does any damage to you. Unlike the above example, it still costs some MP to use unless you want spend some of those extra turns to steal MP from the enemy in some way, but assuming you don't need other forms of healing, you can stay 3 turns ahead of the enemy permanently. However, it does tend to get less effective later on when your characters need higher magic defense for survivability's sake and with too high of a magic defense, you won't be able to inflict Poison on whoever is using this setup on a regular basis, causing them to lag behind from the rest of the party. This obstacle can be somewhat overcome with the Arcanist's Status Ailment Amplification ability, though it will still miss on caster classes on occasion.
Swordmaster/Pirate: Free Lunch, which makes your skills cost no MP to use for two turns and Double Damage/Amped Strike, which do 2 and 4 times your normal physical attack damage but cost 25% and 50% of your MP to use respectively. It's also one of the first of the Game Breaker combos you can get (Chapter 3) and makes all other combinations almost entirely irrelevant. A party with 3 of these plus a Spiritmaster/White Mage combo can curbstomp their way through anything that isn't immune to physical damage.
Pirate itself is a pretty powerful job, and with the right setup (such as a Natural Talent monk), can do 9999 damage early on multiple times in a single turn. It's fairly useful as well, with the various debuffs weakening your enemies.
Spiritmaster is probably one of the most exploitable jobs in the game: Enigma means elemental attacks do nothing, Fairy Ward completely blocks statuses (including self-inflicted ones, such as Life or Death from the Dark Knight, meaning the latter can boost itself to 150% in every stat for free), Stillness is probably the most scandalous one, since it means the player, if they can manage to be faster than the boss, just has to attack, cast stillness before the boss can act, buff themselves until it runs out, then attack, then cast stillness... It's recommended to couple it with Fairy Ward though since it doesn't block statuses. Coupled with a Performer/Freelancer, it can be pulled off from the very first turn.
Dark Knight/Spell Fencer: Drain completely mitigates the Dark Knight's Cast from Hit Points handicap (unless you're pitted against an Undead), meaning the player can use Rage (which spams Black Bane on enemies up to 5 times or until their HP drops to 1) with impunity. The Dark Knight is also a rather powerful class, and three uses of Black Bane easily wipes out most random encounters (save those immune to Dark attacks), which means if the character has Self-Restore from the Vampire class, the player can walk away from most encounters basically unscathed. Furthermore, if you add Templar's BP Limit Up, use the Black Mage/Red Mage combo to get them to maximum BP and follow Rage with Life or Death to restore your BP mid-turn, you can squeeze out 2 additonal Rages for a ridiculous damage potential that's only matched by a very high-leveled Ninja that manages to trigger Swordmaster's Multitask for all of their attacks.
DARK. NEBULA. Dark Nebula is a Dark Knight skill that, for 30% of your health, hits for a ridiculous 4x regular damage to ALL foes. . . with the disadvantage that it hits your units, too. Sounds not worth the payoff. Until you realise that you can combine it with Spiritmaster's Enigma (or equipment that grants immunity to dark, like the Dark Shield) to make it more efficient than even special moves... or just give them the Red Mage's "Revenge" and let them take the hit for free BP. If your entire party is spamming Dark Nebula, you can triple-Brave every turn and still come out with positive BP. And you can use it with Sword Magic Drain or Freelancer's Mimic to make the health cost essentially moot. Have fun killing endgame bosses in two turns!
Gets even worse when you take the time to set it up with support abilities such as the Monk's Natural talent and buffs such as Lux before hitting Bravely Second. You can reach Bravely Second hitcap with this (a whopping 999,999 damage!) without too much effort. To EVERYTHING. For bonus points, tag the entire party with the Spiritmaster's Adaptation first and watch as your entire party is healed for obscene amounts.
Conjurer: Although it's the last class in the game you can get, Obliterate means you can grind with zero effort as it automatically kills the enemies (save bosses) 20 levels weaker than you and thus consistently triggers every PG, EXP and JP bonus, meaning you'll be getting 50% more of each after 10 battles in a row. Conviniently enough, it also comes with an ability that increases the EXP you get from enemies, although by that point you've probably saved enough cash for a Growth Egg that does it better and doesn't stack with the ability, not to mention EXP is probably the one thing you'll need the least of as described on the main page.
Merchant: BP drink is hilariously powerful since money is rather easily accessible (see the tricks below). Pharmacy is also totally effective against anything Undead, as it lets you buy as many Phoenix Downs in-battle as you want for a piddling 100 pg each. If you know a certain trope, you'll know why this is so useful.
The Mammon Elixir glitch: One of the Nemeses accessible in the Norende Village, Mammon (lvl 25), carries either an Ether or a debug Elixir (its effects are the same but it's listed separately from the regular ones), which can be stolen, then sold for 25 000 PG (instead of the mere 1875 PG from the normal ones). Since one can run away from Nemeses fights, the player just has to challenge Mammon, steal it, then flee, and do it over and over to rapidly build up a fortune. Square-Enix stopped distributing Elixir Mammons; although the existing ones can still be spread by players.
Merchant's Big Pharma restores the target's HP and nets you as many PG as the HP restored. With the right battle setup, you can just leave the game running on autobattle for several hours and walk back to several million PG. One of the easiest ways is to combine it with a Vampire's Chomp, which reduces the target's HP to 1, on an enemy with a lot of HP and little offense, plus any kind of MP-free healing. But if you can find an enemy that you can trap in a non-damaging loop, all you need is one ally whose basic attack deals slightly less damage than Big Pharma heals. With Abilink, this can be set up as early as the Wind Temple.
Low Leverage, another one of the Merchant's abilities halves the cost, damage, and recovery of both your and your opponent's abilities. While it may not sound like much, it means that you are much less likely to get TPKed. Once you start hitting the damage cap it becomes even more useful: say you've designed a very formidable party that hits for 15000 damage per attack (a conservative amount) the extra 5000 damage is lost, however with low leverage in effect your damage output is reduced by one quarter (to 7500) and your cost is halved. Furthermore it allows you to spam the aforementioned My Hero/Mimic every turn.
Arcanist + anything that can cause Poison (either Black Mage, Red Mage, Spellfencer, Salve-Maker, or Vampire) cheeses anything that isn't immune to Poison (which is actually a lot, including the majority of the bosses): Hit them with Poison, then Exterminate for over 7000 damage. (9000 if Gloom is equipped, and it doesn't have resistances and/or high magic defenses... though it will usually still do more than anything could heal.) It may actually be one of the greatest things overall, due to how bosses work - the 'High-Jump Hasten World' combo isn't ALWAYS infallible, and a lot of the other strategies rely on the foe using either single target attacks or doing something very specific that CAN mess up. Arcanist isn't like this- the key to the Arcanist's entire strategy is Poison. Normally, people would just forget about Arcanist at that point because most RPGS have taught us status affects are useless for the player to use. After all, what boss can be poisoned? Most, actually. The great thing about Bravely Default is a majority of the bosses are human. Almost every human, save some specific humans such as Qada who revolve their strategies around being partially healers, are susceptible to poison. Give it a couple of turns, and eventually poison WILL work. And when it does, Exterminate rips bosses apart. This is what makes Arcanist so formidable: it isn't about reacting to bosses or relying on specific markers, it's just about having someone shield the Arcanist, having a healer ready, and the Arcanist itself.
Some bosses, like the Templar, are only able to attack one party member at a time. The Ninja learns an ability to force an enemy to target a particular teammate that they can cast every turn for no cost. The Swordmaster learns an ability that allows them to nominate one enemy against whom they will perform a hugely powerful counter attack against a selected enemy if attacked that by them that turn, which also has no cost. With another party member on healing duty, you can shut them down entirely. Or if you really want to break some bosses, giver that Swordmaster the Spell Fencer's Drain ability or a blood sword, now every counter attack will likely fully heal them which means both that you don't need to waste a turn healing them and that any attack that doesn't either one shot the samurai or bypass counter will be utterly negated no matter how many are used in a row. Slap a ribbon on them and there is very little that can stop them (with the added benefit of single target status spells like Death being focused onto the one party member who's now immune).
As mentioned above, Time Mage's Hasten World can really break the game in half to a degree that even the strongest Bonus Boss can be defeated by setting the game on autobattle: it increases the amount of BP gained per turn to 2 for both allies and enemies, which can allow you do things like spam Valkyrie's High Jump on an enemy that's completely unable to do anything about it since the party collectively blasts off at every chance they get before the enemy can get a turn in, or making sure that the Spiritmaster can spam Stillness right when it wears off.
At the very least in the demo, there's a powerful combo that renders most fights a breeze: The Ninja's Utsusemi Ninjutsu (One free evade) and Transience ability (Counter at double power with a successful evasion) combined with the Red Mage's Turn Tables ability (Bonus BP when evading) keeps your party from most damage while still enabling them to attack multiple times in a turn. The only danger for this combo comes from magic-wielding monsters (of which there are few in the demo) and monsters that attack multiple times in a turn (which can be healed during their negative BP turns).
The Utsusemi combo also completely breaks several bosses that only have physical attacks and never Brave, such as the keystone dragons. Combine Utsusemi with Ringabel (best agility) and Hermes Sandals (+10 agility), use Utsusemi once, hit Y to auto-battle, and walk away and get a snack. While it does rob your other party members of EXP/JP, you can always grind later.
Also in the demo, a Valkyrie with Crescent Moon, 2-Handed and a Mythril Spear on your fastest character can make gaining PQ, EXP and JP ridiculously fast and easy. With this setup, go to the southern part of the map, past the dungeon to a little shore. There you will always encounter 6 Chompers which are pretty strong, can poison you, but usually run away. Use Brave to have your fastest character cast two Crescent Moons and watch them all go down before they can even blink. Keep at it for a while and soon you'll be gaining 120 Job Points a fight. (Also recommended to have your 2nd fastest character do the same thing in case the first fails to KO them all. As long as they attack before the enemy gets a chance to act, you win.)
Here's another one if you need money and XP. Simply set a character as a Ranger or Ninja, perhaps one of each, and give both of them Sword Magic with the Merchants More Money which allows you to get more money and it stacks with others. Simply use a full four braves, using the first on both to add the enemies weak element and then do attack and watch as you murder enemies and get massive amounts of gold!
Templar: Rampart can make several tedious bosses, such as the dragons to open Vampire Castle, into little more than setting the game on autobattle and waiting for them to die, since when combined with the aforementioned Hasten World, it can be cast every turn for no mana. It turns pretty much any boss reliant on physical attacks into a pushover.
The Rise From Dead auto-ability. It has a very high success rate (at least 50%) and strongly mitigates the disadvantages of using the low HP enhanced attacks like minus-strike provided you keep at least one character with HP higher than the relevant boss can one shot and frees your white mage up for other things. For added fun See You in Hell can also be equipped.
Arguably the most game breaking combo for the final bosses is Two Monks with the Dark Knight skills, a White Mage with the Spiritmaster's skills and Hasten World, and a Pirate. The set up is rather easy: Have the each character use enough brave to have -4 and employ Stillness to go two whole turns of not being damaged while you whittle away their HP using a combination of the Monk's PhoenixFlight then spam Minus Strike to deal a full 9999 damage through the entire fight. Thanks to Stillness and the Pirate's Shin Smash, which lowers speed, they party won't be damaged since their attacks will be faster than the enemy.
Three Monks with Vampirism skills, and a Vampire with Medication skills. Set Natural Talent, HP 20% Up, Drain Attack Up and Rise From Dead to your three Monks, and HP 20% Up, Drain Attack Up, Rise From Dead and anything that increases speed on your Vampire. When a battle starts, set your Monks to use Blood Thirst, and your Vampire to Brave to max and use Compounding to mix Beast Liver and Dragon Fang to make Giant's Drafts for your party. Nothing will be able to kill you short of instant death attacks, with even those being negated by Rise From Dead, and any damage you take you'll instantly recover with Blood Thirst, which is based off of regular damage, which itself is increased by using Natural Talent. There are only two drawbacks to this method. The first is that your Vampire won't be doing any significant damage (no Natural Talent), and they'll usually be the one dying often. The second is that this makes fighting dreadfully boring.
The Vampire's Battle Thirst can be pretty debilitating to normal enemies if done right. With Drain Attack Up, it will steal 2 BP instead of 1, and if you can get all enemies in the battle down to -4 BP before they can act...they will never get to do so, because you can just keep draining their BP when they start getting close to 0. You usually won't even run out of MP, thanks to Magic Thirst.
As mentioned under Metal Slime on the main page, there is an enemy that you can steal Megalixirs from that you can repeatedly encounter. This is game-breaking enough on its own, considering that it's not that hard to maximize your stock of them, but the Salve-Maker has an ability—Turn Toxic—that lets you make a healing item do damage instead. So you could have four people with the relevant skillset and have them each Brave 4 times and spam a total of 16 toxic Megalixirs, dealing 159,984 damage to every enemy in the battlenote To put that into perspective, the final boss only has 202,500 health., or potentially even more if you use Bravely Second with Attack Item Amp active (which makes attack items do 1.5x damage, thereby making each Megalixir used during Bravely Second do 14,998 damage to every enemy instead of 9999). In fact, if you can manage to manipulate the turn order precisely enough, that could theoretically be done with one Megalixir and 15 uses of Mimic.
Blessed Shields and Sage's staff until you need better healing later on, are very good equipment for a good majority of the game. Blessed Shield, if used as an item, casts Cura. Note, it isn't used up. You can keep on using them. Sage's staff is the same, except with Raise. Free revives. For a good while you can go without a dedicated healing class, or at least have one but not be required to equip red or white magic. They even go well together as using the items counts towards the requirements for the staff's special moves, which are very useful as well.
Especially after **For the sequel** allowed you to speed up battle animations, special moves become really powerful and useful. They are powerful moves or other effects that also give a set buff to your party. The buff lasts until the music ends, and the music doesn't speed up when the animation is sped up, so you can go more turns with the buffs. The buffs can stack and have higher caps than normal buffs, and if you do another special move, the music keeps going. The game refers to this as chaining specials, and with the right set up, this can be absolutely devastating. You can even steamroll through the majority of the game without specific class set ups, only relying on the weapons as special moves are tied to them.
A good example using only one weapon on each character is Staff, Katana, Knuckles and Rod: Staff can lead the battle with a Lux, giving buffs to your party. Which buff in particular? Attach a crit rate up and watch your party get 1000% critical hit rate, which equates to absolutely guaranteed. If you want to attach another buff, that's fine- the Katana also has a critical hit rate buffing special in Breaking Wave. Not as much as Lux, but not getting a critical hit with it is rare. Next is the Rod, with which you can cast Withering Ripple and debuff the enemy. If you're so inclined, you can even attach an effect that lowers resistance to status and then inflict that status either with spells, or with attack specials that have that status attached. Finally, the knuckles. Slap a Knuckle Lore skill on the Knuckle user and they should be incredibly powerful. If by that point in the game your critical hits don't already hit the damage cap, not to worry. The Katana's level 1 special increases strength. So does the Knuckles' level 1 special. The level 2 special increases hit rate, meaning even more damage with normal attacks. How do the Knuckles' specials activate? Through critical hits. Only 3 for level 1, only 6 for level 2. You can attack every turn, or default to max BP and then unload and get your specials instantly, then use it the next time you attack. The knuckle user will have a really high damage output, the Katana can supplement it with their own specials, the rod and staff users can stick to healing. Especially the staff user, who can cast rejuvenate every 5 heals, get Norende advanced enough and Rejuvenate should heal you completely, revive any dead party members, restore all your MP and give 3 BP. For extra fun, poison the enemy as well, or have the mage cast offensive magic with critical magic equipped. For an even less foolproof plan, give the rod and Katana users staffs in their other hand so they also have access to Lux and Rejuvenate, have them heal every turn regardless if it's necessary or not and rejuvenate as much as possible, and you have a constantly regenerating party that regularly hits the damage cap, is constantly buffed and the enemy debuffed.
Wanna know how to get unlimited money and experience/job points?
Step 1. Obtain the Conjurer job and grind until you gain the Obliterate ability and equip it (obliterate instakills enemies at the beginning of the battle that are more than or equal to 20 levels lower than you)
Step 2: Go to an area with powerful monsters in it (like say, the northern forest)
Step 3: Turn the encounter rate up to max
Step 4: Because of the way bonuses work, Obliterate will give you bonuses in experience, job points and money for merely entering battle that keep stacking up after each successful battle (until you hit the limit of course).
Step 5: Enjoy obtaining absurd amounts of money, level ups and as much mastered jobs as you want. Bosses from this point onwards may as well surrender in advance to avoid humiliation.
Freelancer's Stand Ground gives you a whopping 75% chance to keep your last HP where you'd normally get KO'ed - but won't activate if you have only 1 HP left. Combine this with Salve-Maker's Auto-Potion for automatically raising this 1 HP to 151 HP and getting ready for the next attack !
Equipping the Blood Blade lets you cast Sword Magic Drain for free. You'll probably only get one, but unequipping it is a free action, and doesn't cancel a queued Drain spell. Scroll back up and count how many other game-breakers are reliant on or enhanced by Drain.