Wake Up Call Boss

4 vs. Satan:
*The first knight-battle. If you didn't level enough, you might as well lose this battle.
Alex in Princess Quest:
*NONE
The Stone of Power:
*NONE
The Three Kingdoms
*NONE
Dragondawn
*NONE
Harter Knall
*NONE
Hero Story
*General Hosse. Unlike the Ogre, this one is pretty challenging.
Kill the Demons
*It becomes gradually harder with bosses. The final ones require luck and strategy even. Three come into mind, though. The first is the Shaman, who has two helpers and poisons the party (which has only two at that point) repeatedly.
*The second is the Ogre, as he has stronger attacks than the previous bosses and is the first with 1000+ HP.
*The last one is the Ice Golem, as the previous bosses were mostly pushovers, while he has over 3000 HP and defense against non-natural weaknesses. (Thunder, in this case.)
Satan Saga
*The second battle with Garith where you only have three party members.
Story of Hero:
*NONE
The Legend of Devils
* The Snake Leader. Unlike the first two bosses, which are push-overs, this one most likely WILL wipe out your party unless you managed to save some antidotes until you get there. Fortunately, it is a Glass Cannon with "only" 330 HP, so if Marron is equipped properly once the two minions are offed, hope it doesn't evade your attacks too often.
* Darrol could be one for the entire game. While the previous monsters could be easily out-levelled, this one uses devastating attacks. And yes, he's the game's first clue that you will see it more often.
The Sidestory Duology:
*NONE
The Time Of Bloody Fear:
*NONE