Sour Bill was King Candy's minion, trusted adviser, and polar opposite. While King Candy was eccentric, loud, cheerful, and rambunctious; Sour Bill was quiet, brooding, reserved, and downright.
The two were evidently close and practically inseparable at many points throughout the film, with Sour Bill appearing to be the only character King Candy has any trust in; having complete knowledge of the king's villainy, the game's codes, and the truth behind Vanellope, to a partial degree. Interestingly, whilst every other character had their memories locked away after King Candy took over, Sour Bill retained some of his, for reasons unknown, though it's most likely because of his close relationship with the king.
Sour Bill was also the second most powerful figure in the game, as he's seen taking part in King Candy's duties from the Random Roster Race opening ceremony all the way to interrogations, is left in charge of the castle during Candy's absence at one point, and has the power to imprison who he pleases, as seen when he imprisoned Fix-It Felix in the fungeon. Whether or not Sour Bill was personally antagonistic, himself, or merely following orders out of fear or respect, is unknown. However, he notably doesn't appear to have any fear of King Candy, unlike the other henchmen seen, nor is Candy ever abusive or brash towards the sour ball, a trait that's fairly rare in Disney villains; so all in all, the true relationship between King Candy and Sour Bill is left ambiguous, though because of points shown in the film, itself, they appear to be on rather good terms up until Candy's ultimate demise.
Taffyta has a lot of respect and admiration for King Candy, her ruler and the only racer ranking higher than herself.
The relationship between King Candy and Vanellope, by all accounts, is incredibly hateful, filled with bitterness and jealousy. Though they have little screen time together, their feelings toward one another is more than apparent and prominently shown throughout the film.
King Candy, as explained above, is actually Turbo, who hijacked Sugar Rush to become the game's central character and retain the extreme popularity he once had in his old game, TurboTime. With Vanellope being Sugar Rush's primary character, she instantly became Turbo's rival, and remained so for years up until his death. This fact appears to be the only true reason the rivalry between the two exist, and because of King Candy's insanity, it's a deadly one, nonetheless, as he was shown to have made two attempts at the nine-year old's life; once when he tried to delete her code, and again when he tried to ram her into a large stalagmite.
Vanellope's views on the king aren't exactly shown as clearly as the other, though she appears to view him as a cruel ruler and enjoys mocking and annoying him when given the chance, as seen during the Random Roster Race. Even so, she does show a fear of him whenever he loses his temper and attacks, once again hinting a brutal history between the villain's fifteen-year reign.
Upon meeting each other, King Candy and Ralph where immediately enemies. Ralph took a disliking to Candy after the latter denied his medal. As time goes on, the two rivals' hatred for each other grew stronger and stronger, to the point where Ralph mindlessely wanted to pummel Candy, and where Candy attempted to murder Ralph after the former became a Cy-Bug. Though the two are completely different in personality and nature, their stories are similar. Both Ralph and King Candy's, then known as Turbo, game-jumping actions to change their lives brought misfortune to the arcade, though Ralph's ambitions were driven out of wanting a better life, and he decided to right the wrongs he committed. Meanwhile, Turbo only wanted the attention another game was getting, ruining the game out of pure envy, and instead of trying to fix what he did wrong, he took over another game and ruined the life of another character and caused her great misery, with no remorse.
All-in-all, despite Turbo and Ralph's short lived rivalry due to Turbo's death, Ralph is Turbo's greatest and most hated enemy (apart from Vanellope).