How to handle potentially large (50+ values) check list?

So I have a check list in a form that becomes populated with choices based on some data attached to the user accessing that page. It will have around around 50 values in most cases, but can be as little as one or two. Furthermore, if an Admin account navigates to the page there will be hundreds of values.

The only real criteria for this input is that it can handle multi-select and select/deselect all.

My original plan was to do a small scrollable box with the fields, but this could be unintuitive if there are 300 options to choose from. I was also looking into Bootstrap-Select with its select/deselect options, but I can't quite get it to work on my asp.net MVC application.

Any recommendations on how to handle this list?