When I've played Sonny 1, I got stuck at Zone 4, where at the first level some wizard casts "Doom" on you, killing you in 2 turns or so.
But Sonny 2 was very easy. I got to something like level 21, and slaughtered the Mayor and his pet Hydra (Or whatever) in a few turns. Is there any catch to this game?
Yep, I agree with you. Sonny 2's easy difficulty is very easy. Try Challenging or Heroic, like everyone else is. I'm currently on Heroic, and I'm still on the Tunnel of Illusions. I'm trying to unlock the Corruptor, which can appear if you defeat Heroic difficulty, without doing training fights and without repeating any defeated bosses!
Yonkid, 25k damage is only achievable in when you are about 10 or more levels above your enemy, and preferably in easy, or the enemy has an effect that renders you to deal more damage. Believe me, on a legend run you don't hit over 1000 often.