The abusers could face legal consequences within the wizarding world. Sirius might report them to the proper authorities, like the Ministry of Magic. And if it's the Dursleys, they could lose their guardianship of Harry. Also, their reputation in the wizarding community could be severely damaged, as Sirius would likely spread the word about what they've done.
Sirius might use magic to punish them. He could hex them or use some other form of magic to make them feel the pain they inflicted on Harry.
One possible consequence is that Sirius could make their lives a living hell. He has a fierce temper and a strong sense of loyalty to Harry. He might constantly intimidate the abusers, making them fear for their safety. If they are at Hogwarts, they could be expelled. And in the long run, they would have to live with the guilt and shame of what they've done, especially if the wizarding community shuns them for their actions.
Chapter 123 is the strongest chapter-level answer because it starts from After He Yun also carefully rolled up her trouser legs and walked down... and follows through on Seeing this, He Yun chuckled softly to himself, then glanced at his own....
A practical answer is Chapter 152, because it turns the idea into a concrete scene. The chapter opens with While most of the villagers of Chixia Village were gathered at the village..., adds pressure through Is every man in the world supposed to be hers?], and ends on That shouldn't be." Zhao.
The best chapter pointer here is Chapter 133, "Teacher Du, Please Reconsider the Termination of the Contract". It opens with Watching Jiang Li and the others finish their meal and tidy up the table,... and closes on It was only after she shared the concept and purpose of the show with him....
A practical answer is Chapter 112, because it turns the idea into a concrete scene. The chapter opens with These five people are supposed to be at odds., adds pressure through Do you remember that bowl of Mushroom Soup?" Jiang Li smiled, "Your..., and ends on [Hahahaha why is the Princess starting.
Look to Chapter 95 for the clearest answer. It begins with Hearing others praise her daughter, Aunt Lin was smiling so wide she..., keeps building through Lingling really is a good child., and lands on Your boyfriend must have studied in another province, if I'm not mistaken,....
The best chapter pointer here is Chapter 94, "Finally, Someone Comes to Calculate Affection!". It opens with Jiang Li really has some skills, being able to figure that out." "Can the... and closes on Brother is going to dress you up; look how pretty this outfit is."....
The best chapter pointer here is Chapter 140, "Did Jiang Li Finally Crash?". It opens with In the evening, the setting sun was like blood, dyeing the entire earth a... and closes on I was just joking, just joking." Seeing that Wen Jiaojiao had no intention....
The best chapter pointer here is Chapter 141, "The Recruitment Contest!". It opens with It had happened in the afternoon when Aunt Ying's son and daughter heard... and closes on Jiang Li couldn't help but laugh and cry..
The best chapter pointer here is Chapter 111, "From now on, Zhao Daniu is my new brother!". It opens with The main room's door was pushed open just a crack, and the head of the... and closes on This time it was in a dream..
If you want the clearest chapter reference, go to Chapter 84. Early on, When the villagers tasted his curry beef one by one, their faces revealed...; later, the chapter leans on In the end, he could only secure a score of 5..