I recently wrote a command-line utility lemmyverse to find communities indexed by Lemmy Explorer. A quick count shows almost 14%(!) of all communities indexed by lemmyverse are junk communities created by a single user @LMAO (reported here):

% lemmyverse . | wc -l
  30376
% lemmyverse enoweiooe | wc -l
   4206

Here's a python script, using no external dependencies, which uses Lemmy's HTTP API to delete all communities that @LMAO moderates:

#!/usr/bin/env python

import json
import urllib.parse
import urllib.request

baseurl = "https://lemmy.world"
username = "admin"
password = "password"

def login(user, passwd):
	url = baseurl+"/api/v3/user/login"
	body = urllib.parse.urlencode({
		"username_or_email": user,
		"password": passwd,
	})
	resp = urllib.request.urlopen(url, body.encode())
	j = json.load(resp)
	return j["jwt"]

def get_user(name):
	query = urllib.parse.urlencode({"username": name})
	resp = urllib.request.urlopen(baseurl+"/api/v3/user?"+query)
	return json.load(resp)

def delete_community(token, id):
	url = baseurl+"/api/v3/community/delete"
	params = {
		"auth": token,
		"community_id": id,
	}
	body = urllib.parse.urlencode(params)
	urllib.request.urlopen(url, body.encode())

token = login(username, password)
user = get_user("LMAO")
for community in user["moderates"]:
	id = community["community"]["id"]
	try:
		delete_community(token, id)
	except Exception as err:
		print("delete community id %d: %s" % (id, err))

Change username and password on lines 8 and 9 to suit.

Hope that helps! :) Thanks for the work you all put in to running this popular instance.