I feel like he got a lot of character through the world itself. Team Skull is made of people who either couldn't pass thebisland challenge or quit, Guzma wants revenge against the cpatains and Kahuna's that look down on him and his group. He has an attraction to Lusamine because out of everyone he has met he has never met she is someone that has treated him with any amount of love or respect. All of the people he has working for him care for him so much that they are willing to gang up on you to save their boss and even beg you pretty much. When he was younger he entered many contests but always got third place except for one time when he won second, He ran away from home when he was young because of his constant failures, and every time you beat him, he gets mad at HIMSELF instead of at you. He wants to be a captain or something close to it and he is determined to be a master of Bug Pokemon to the point he hordes every Bug Z Crystal they can find. Guzma has severe self esteem issues, and an inferiority complex. From everything I picked up about him from this game he acts confident and tough but when he is alone he is probably one of the saddest people in the whole series. His whole life has been nothing but a series of failures that he couldn't even stand to try again and risk another loss. There is also the implication that his dad beat him as a kid and when he grew up he took revenge on his dad via the golf clubs in the shed. Now before you scream murder, His dad is very much alive and even tells you "I tried to set that boy straight, but I got beat instead".