The ending to the pachinko arc is very uplifting. After finally defeating Ichijou and "the bog", Kaiji, Sakazaki and Endou laugh, cry and hug each other. They then spend the night drinking and sharing the money that they just won evenly. Kaiji is able to pay off his debts and even release his friends, Sakazaki can finally start over and Endou won't have to worry about Teiai Corporation anymore. Made even better by the fact that Endou was previously a villain.
From season 1, episode 9: "I want to free that man with all this money."
The end of Season 2, The 45ers reunite on the surface. Mirai wa bokura no te no naka!