I've made a class and assigned hundreds of lessons for my 40+ friends for LearnStorm, including 20+ Grammar lessons to everyone. One of them asked me to remove their Grammar assignments, but it looks like the only way to do this is to manually edit every Grammar assignment and remove the user from the assignment.
I think having an option to bulk delete assignments from a individual user would be a huge improvement. Here's an existing page for viewing student stats, this would be the perfect place to add the deleting options:
(I got to this page by viewing the Assignments tab, and clicking on a user)