Fu-xi

Lord Fu-xi (Voiced by Dwight Schultz) Once, Fu-xi was a brave and noble warrior, regarded by many snakes as a hero and treated like a lord. Fu-xi defended others with his incredible skills and fear-inducing venom. But when others regarded him and his kind with paranoia and hate, Fu-xi changed for the worst, taking on a racist hatred towards "two-leggers" in retaliation for their violence and persecution.

He came to view himself as a defender of serpents, considering the ones that went along with him as his brethren, but having expectations of his kind, saying they should be strike fear into "two-leggers", and to be prepared to strike at them by any means necessary.

Fu-xi fights with a very similar style to Master Viper, with lightning fast moves, but he also incorporates biting to deliver his fear-inducing venom into his opponents/victims.

Viper.
Fu-xi saved Viper from some paranoid villagers who attacked her simply for being a snake, and revealed he'd heard of her, the "Great Master Viper of the Jade Palace", addressing her as "little sister", for in her he saw a potential ally/apprentice.

He subtly demeaned her a few times for fighting for "two-leggers", trying to convince her she should fight against them and side with him. However, trusting Viper just for being a fellow snake proved to be his downfall.

Po.
Fu-xi regarded Po as just another "two-legger" to get rid of, and used his unfavorable comments about snakes in efforts to sway Viper to his side, and he violently tried many times to kill him.