I'm a mod on r/DoctorWho and a few other places and have some experience in using the Reddit API. I gave an initial concept idea here for an initial banning spree, but since then, I've had a couple additional ideas. It's nothing amazing but I have a bot and I can easily add something based to that and bannings could start post haste, both as a one-off or as a continuous feature. Let us make the Almighty Thanos's plan a reality!

Edit: Would people prefer grabbing the entire list and then banning people or do it in batches of say 10/100/whatever? Also, would people be interested in being able to message the bot for a /r/thanosdidnothingwrong equivalent of http://didthanoskill.me?

Edit 2: Reminder (since I've seen it a few times since): You cannot get the list of subscribers and banning does not affect subscriptions. Aside from a drop in activity, edits and posts elsewhere, there would be no public sign of this happening.