I'm not sure of the exact ones, but you can search on fanfiction platforms like FanFiction.net or Archive of Our Own. Look for tags like 'neglected Harry' and 'Slytherin Harry' to find similar stories.
Search for fanfictions that deal with alternate versions of Harry. Some might explore his character in a different Hogwarts house or with a different personality due to some form of trauma like neglect. You can also check out some of the more popular authors in the Harry Potter fanfiction genre and see if they have written anything similar.
There might be some out there that focus on a darker or more changed Harry. You could try asking in Harry Potter fanfiction communities. They often have members who are well - read in different types of fanfictions and can recommend ones similar to 'neglected harry is a cold slytherin' based on the themes of neglect and a different Harry in Slytherin.
There are some fanfictions that are related in theme. For example, 'Lost Naruto in MLP' where the Naruto character is lost in the MLP world and has to deal with various situations that could be somewhat similar to being neglected. Also, 'Stranger Naruto in Ponyville' might be a good one. In this, the Naruto character is like a stranger in the MLP world and may face some form of isolation or lack of understanding which is related to the idea of being neglected. And 'Alone Naruto in Equestria' where the Naruto character is alone in the MLP world which has a connection to the neglect aspect.
Well, in this 'neglected harry is a cold slytherin fanfiction', the change in Harry's house could lead to different relationships. He might form alliances with characters who were previously his enemies in the original story. His coldness could be a defense mechanism due to the neglect he faced. And it could show a different side of the Slytherin house, perhaps not all of them are as bad as they seem in the original when Harry is part of it.
One common theme is the idea of isolation. Since Harry is cold and in Slytherin, he often isolates himself from others, whether it's his old Gryffindor friends or new Slytherin acquaintances. Another theme is redemption. His coldness might be seen as a negative trait at first, but as the story progresses, he might start to show more warmth and redeem himself in the eyes of others.
I'm not able to directly recommend ones similar to it. However, you can search on fanfiction platforms using tags like 'Avengers, alternate universe, dark theme'. This might help you find fanfictions that are in the same vein as 'hell is cold avengers fanfiction'. Maybe there are some that explore the Avengers in a desolate or harsh setting which could be somewhat similar.
One great 'Harry is a Slytherin' fanfiction is 'The Slytherin Heir'. It shows a different side of Harry, exploring how he navigates the Slytherin house with all its politics and prejudices. The characters are well - developed, and it has an interesting plot that keeps you hooked.
One popular 'Abused Harry in Slytherin' fanfiction is 'The Slytherin Heir'. In this story, Harry faces abuse within the Slytherin house but overcomes it with his own strength and the help of some unexpected allies. It has an interesting take on the Hogwarts dynamics.
One popular 'Harry is a cold Slytherin' fanfiction is 'The Slytherin Prince'. In this fic, Harry's character is reimagined as a cold and calculating Slytherin. He uses his intelligence and cunning in ways that are different from the canon. It delves into the complex relationships within Slytherin house and how Harry navigates them while still maintaining his cold exterior.
There's 'Fem Harry Potter and the New Hogwarts'. It also reimagines Harry as a female and has some interesting twists on the original story, like different relationships with the other characters.
There's 'Harry and the Founders' Legacy' which also has Harry in a role related to the founders. It has a really cool plot where Harry discovers ancient secrets about the founders that change his view of Hogwarts.
You could try 'Harry in the World of Hunters' which also has a similar concept of Harry being involved in a hunter - like world.