Good Passive: May get a critical hit when attacking that gives +25% AT before damage calculation.
Bad Passive: Magic Attack and Field Magic have a chance to misfire and have no effect (They still get used up).
Knight
+2 Defense every level
Good Passive: May get a critical guard when defending that gives +25% DF before damage calculation.
Bad Passive: When defending in a fight, may fail to dodge or escape. (The flavor text states that the armor is too heavy, this is regardless of the actual armor being worn)
Thief
+2 Speed every level
Good Passive: May get to see the battle cards face up before a fight.
Good Passive: During a fight, has a chance to dodge the enemy's attack even if they have a higher speed.
Good Passive: May dodge the traps set on the map or the traps inside red chests.
Bad Passive: When an attack is not dodged, it may become critical and deal extra damage.
Mage
+2 Magic every level
Good Passive: When using attack magic in a fight, the magical power increases and may cause more damage than usual.
Bad Passive: When you select "Attack" or "Strike" during battle, may get -25% AT before damage calculation.