under the snake flag

Prehistory (4th year)
After Harry's name was dropped from the Goblet of Fire, Gryffindor declared a silent boycott. His sporadic attempts to justify himself met with a wall of misunderstanding, and Potter quickly stopped intruding. Noticing the "golden boy's" isolation, Draco Malfoy—not without hidden interest and prodding from the older Slytherins—offered Harry neutrality, which blossomed into a secret friendship.
Harry gradually entered the Slytherin circle. He spent evenings in the dungeon common room, socializing not only with his peers (Draco, Blaise Zabini, Theodore Nott, Pansy Parkinson, Tracy Davis, Daphne Greengrass) but also with older students—Marcus Flint and Casey Warrington. His elders taught him pragmatism, the rigors of dueling, and an understanding of pureblood politics, while his peers imparted what Gryffindor had not—honor of word and respect for personal boundaries.
At the same time, Harry realized the truth about his past environment:
Ron Weasley feigned friendship in exchange for regular payments from the funds allocated by Dumbledore "for the upkeep of the hero."
Hermione Granger acts as a "warden" in exchange for Dumbledore's promise to make her the youngest and most celebrated Muggle-born witch of the century by giving her access to the Ministry's restricted archives.
The Plot (Beginning of 5th Year)
Following the Dementor attack in Little Whinging, the Ministry holds a trial. Dumbledore formally defends Harry, but resorts to a legal ploy: Potter's status as a Hogwarts student is revoked until the Wizengamot decides. Because of this procedural error, Harry is required to undergo the Sorting procedure again upon his arrival at school.
The hat barely touches the head of the changed Harry - and sends him to Slytherin.

In this universe, Harry won't be a loser. He'll be a manipulator, he'll pretend to be a good person, and he'll gain Dolores Umbridge's trust, so she'll appoint him head of the inspection squad.