Not so sure about that, mostly because a Task/Issue >> Assignments is a One >> Many relationship, since a task/issue can be assigned to more than one user/role/team. So if one task is assigned to two users, that generates two assignments. Either one of those users could be the "last" assignment made and would probably appear to be arbitrary.
If you are using this report in a Dashboard Custom Section (report rows automatically filtering to the work object being viewed):
I think you could leverage an Assignment report with no filter (as opposed to a Journal Entry report with an Assignment filter). The Assignment report won't show assignments that have been removed, it will only show current assignments, who made them, when, and who's assigned, etc. If the task is only assigned to one user, then the assignment report will always show just the latest assignment made. If the task is assigned to multiple resources, the report will show the assignment details for each assigned resource. I think the part that speaks to your challenge is that it will be a clean list because won't show assignments that have been removed.
If you are using this as a standalone report:
I still think you're looking at an Assignment report because it can't show assignments that were removed, it can only show assignments that exist right now. The primary benefit of a Journal Entry report is showing historical details, and it seems like you don't need that for this challenge.