Here are the list of enemies that power up and increase their EXP value when certain attacks are used on them, a * beside the enemy name means that it doesn't become stronger, a ^ beside the enemy name means you can only increase its EXP value once:

*^Eye Goo: Blind

*^Mage Goo: Blind

*^Flue Goo: Blind

Goo Count: 3 or more hits dealt on it for more EXP
7 or more hits dealt on it for even more EXP

^Wyd: Use a fire attack to transform it into a Firewyd, and use a water attack to change it back to a Wyd (but why would you want to???)

^Drake: Fire attack

*Bot: Elemental attack(ie: Fire+Wind...)

Legion: Direct attack

Generator: Wind/Water attacks

^Cairn: Earth attack

Lavoid: Fire attack

Orochi: Direct hit

If want you to learn more about Breath of Fire IV, then discuss BoF4 me, and others in the BoF4 forum, here in Neoseeker!