It is a python script, you need the praw library. The client id’s are given in your profile after you create an app.

  
import praw

reddit = praw.Reddit(client_id='yourid',
	client_secret='yoursecret',
	password='your password',
	user_agent='deletes my comments',
	username='your username')

redditor = reddit.redditor("your username")

for comment in redditor.comments.top(limit=10000):
	comment.edit("deleted")
	comment.delete()

You can edit and delete everything in the same pass but I prefer to overwrite my comments first and give time for the cache machines to register my new garbage before deleting with another pass.