Add a link to a lemmy community in every automod comment, make every user manually approved.

Make onerous rules and restrictions. Hold posts for moderation and make them answer questions. Don’t accept the answers. Shadowban regular contributors.

That’s Reddit, so you should solve the problem in a Reddit way: start banning everyone and delete threads. It’ll become empty in no time.

Just walk away, let it crumble, and accept the time and effort you put in are a sunk cost.

Perhaps make a pinned post saying what’s happening and why, a plug for the Fediverse, and leave.

You can do “temporary events” without approval where you just claim there are too many new people and can shut down most posting/commenting for a week. Not sure if there’s an explicit limit, but if you do it too many times they’ll probably take the sub from you.

You can disable video and images, go text-only, and turn off media in comments. You can set the wrong language so it gets surfaced to the wrong people. Max out all “safety filters”. Arbitrarily mute and ban people, and don’t respond or explain why. Become extremely hardline about something stupid, add it to the rules and be as insufferable as possible about it. There will be a lot less oversight if you pretend the changes are you taking some strong moral position on something.

A good one to go for is spam. Basically consider any mention of any brand/product/show/site/etc advertising and pretend everyone is an astroturf bot and be ban happy. Since a large chunk of reddit is actually this it will be hard for admin to figure out when you aren’t acting in good faith. Other good things to go after are kids or adult content, or things that it would look bad for a public company to be defending.

Set up automoderators that remove really broad sets of keywords that could arguably be related to what you’re going after, but are going to have tons of false positives. If the keywords overlap with what the sub is about, even better.

I haven’t delved into the other posts, so sorry if this is a duplication.

What if you make a post saying posts to the sub will now require manual review and as the only mod, you log in occasionally and approve posts.

Probably add some automod restrictions for comments too.

Who knows when you’ll get a chance to approve posts.

Kill it by making it suck. Apply rules unfairly and inconsistently, but in a way that affords plausible deniability (ex: over-apply them to controversial posts/comments and let mostly harmless stuff slide if it gets enough upvotes). Slowly trickle in new rules that narrow the focus of the community to exclude content. Lock posts as soon as any arguments start to kill overall discussion. Be a petty tyrant, bait arguments and ban people for arguing back.

Not every strategy may necessarily be applicable to your sub, but I bet a lot could be!

Your requirements appear to be contradictory. You want to kill it, i.e. not see it any more, and you want to stop moderating it, but you don’t want anyone else to moderate it.

So stop moderating it, and block it. It’s not up to you to tell 200,000 people that they can’t continue to have a community; doing so makes you appear to be acting as some kind of landed gentry. Just walk away and don’t look back.

Can you change the name? Changing it to something radically different would get the job done. Especially if it’s weird and gross

Instead of killing it, what about creating an official sister community here, and encouraging people to use it. Being under the same moderation and having the same rules can go a long way towards establishing that trust. While reddit still won’t like it, it would look terrible on them if they tried to stop it.

Largely, you’d already gotten good advice on how to sabotage a sub.

The key is automod, but don’t forget that the goal is to keep reddit from just undoing it all and replacing you before things get so bad nobody comes back if they do.

So you gotta put some time into it, and implement changes over a few weeks. Start by bumping up the account age setting to something high enough to weed out a lot of casual users but not everyone. Add in some automod filters to remove common things. Let that rest for a day or two, then add in some more filters so that posting becomes harder, but not impossible.

At some point in there, people will complain, so you’ll have to tweak automod to remove references to mods as well.

That’s the process. By the time things get bad enough that reports would get crazy, enough people should have just left in a huff that the reports don’t get so high that reddit pays attention.

By the end of it, any new posts will have to jump though major hoops, so you’ll effectively keep out bots. Place a final automod rule requiring some specific words and walk away. That’s the best you can do. Maybe reddit undoes it, maybe not, but by the time they get around to it, it won’t matter.

Sell it. There are websites for it

Wasn’t there some pop culture subreddit that closed down recently? What was the story/process there?

All subreddits have power posters. The same 6 names show up far more than any other names. You need allies to poison this well, and these are your potential allies. See if you can get some of them in a private non-reddit forum (I dont advocate discord but it is likely easier). Step 2 is adding rules that enable enshittification. Cutting out rumour and requiring reputable sites. Recent news only. Text only posts must contain a question in the title only. No top level replies to own threads. Off topic chat not allowed. AI hating not allowed. I’m sure there are some more. Step 3: inconsistent modding. Apply these rules only to the non-six. Step 4: your allies then start declaring this subreddit dead and that other communities exist. Whilst they move to Lemmy too

I’ve never moderated anything on reddit but…

Can you just change the topic and start deleting posts which do not align with the new topic ?

… or impose complicated rules about what types of posts are allowed on what days of the week / month.

“post titles can only include the letter B on the second Tuesday of each month!”

These types of shenanigans would surely make it a wasteland for new content. I do wonder how long it would take to actually die though. Would people unsub? The user count might just stagnate for ever.