These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Also, his Combination Attack with Kai. With it, you can decimate entire enemy parties in one move without using any MP.
Another game-breaking combo attack is the Pretty Boy Attack (Flik, Alen and Grenseal) which is near guaranteed to do over 1000 damage, thereby killing bosses pretty easily. Also it helps that Flik tends to become a mandatory party member storywise and both Alen and Grenseal are permanently stuck with Rage and Thunder Runes.