Percy Jackson
Dionysus (aka "Mr. D"): Percy primarily has been on Mr. D's bad side from the very second they met. Percy does not like Dionysus very much either, for he constantly antagonizes Percy (and all other demigods, for that matter) by never calling them by their real names (preferring to call him "Peter Johnson" or "Perry Johansson"), but he saves Percy's life in The Titan's Curse. One of the other reasons he may dislike half-bloods is because of the way they treat mortals; he mentions Theseus and Ariadne, Jason and Medea, and alludes to Hercules and Zoё Nightshade in The Titan's Curse, mentioning how the former in all three cases used and later abandoned the latter. However, at the end of the Battle of the Labyrinth, their relationship comes to better terms after one of Dionysus' sons dies in the final battle. Dionysus believes Grover's news of Pan's death, disbands the Council of Cloven Elders when they are at a tie, and cures Chris Rodriguez, a previous traitor half-blood, of the madness he obtained in the Labyrinth. Most shockingly, he calls Percy by his real name, although he later denies this. They are on much better terms by the end of The Battle of the Labyrinth. Although Dionysus denies this, he favours Percy with his judgement, help, and advice, more than any other god in the series. This may be proof that Dionysus is acknowledging Percy, and that their relationship is improving.