Personally, I think the Psychological Class is the best: I beat Sonny 2 with that class in way less than 2 days. I played like 6 hours the first day (call me a no-lifer) and about 4 the next. The second best class I would say in the Hydraulic class.
Dunno why Krin said the Biological class is the best....Or maybe he said: "This class is recommended for Beginners".
Whatever... But if you are starting to play Sonny 2 for the first time, I highly recommend the Psychological class.
In m opinion biological is the best class, i put a lot in str and a bit in vitality so i dont die, with the str my venom atacks get a tone of damage and 3 turns and mob is dead, + i have 3 strong heals, psycological has only 2 and the baron kills him...
Cold style hydrolic is hands down, extremely powerful class. You can stun-silence lock any 1v1 fight with mind freeze-flash freeze. Also ice armor is the best defensive ability in the game.
I've player all classes for few times with best gears , and let me tell u that i 100% sure that Biological is the best class - strongest , fastet , and has coolest skills
It is really based on the situation. Depending on who or what you fight a different class may be more effective. I found Phsycological to be my favorite. Since I could never beat the Baron with any other class and I was setting up BRUTAL attacks that deal up to 3 or 4 times damage.
Warm Hydraulic is the best class hands down. You have to know how to build him with defense. Very few in vitality and the rest in strength = kill them before they even see you