One of the best side quests would be a part of the quest called “Family Matters” in Witcher 3. Geralt of Rivia, on his quest to find information about a certain someone, came across the Bloody Baron who offered him information about that someone in exchange for a favour. The favour was to find out the whereabouts of his missing wife and daughter. Except soon Geralt discovered they werent missing - they had left the Baron because he used to hit his wife and used to drink all the time. Upon confrontation the Baron revealed that his wife had cheated on him when he was gone for a long time because of war. When the Baron found out about his wife’s lover and killed him in a rage, his wife almost killed him and from then on started a two-sided fighting that never stopped, and he became a bad drunk, until the wife finally left with their daughter. Geralt went on to find out about his wife and daughter. He found that the Baron’s daughter and wife had been separated by three witches called the Crones. The daughter escaped to a city safe and sound. The wife however had been captured by The Crones because she had once asked for their help to make the child she was pregnant with disappear. In return she was to become their slave. Now as a slave she was nurturing some war orphans who later became the crones’ meal. When Geralt passed all this information to the Baron he decided to mend his ways and save her from the crones’ clutches. The Baron travelled to the orphanage and with Geralt's help found his wife. At the orphanage, they ran into the Baron’s daughter, who wasn't too pleased to see her father there. His wife had lost her mind because of the loss of the little orphans and was babbling about nonsense. The Baron, filled with regret and sincerely wanting to make up for everything, decided to take his wife to the Blue Mountains where a powerful hermit lived, in hopes he could cure her. His daughter, who couldn't go with them due to other obligations, made her father swear he'd take care of her mother. Geralt, the Baron and his daughter then fought small mosnters and a powerful monster sent by the Crones and after succesfully defeating it, each went their way.