Views - Group by "comment" type, filter by "latest reply by end user"

I would like a view where (1) I can group "comment" type (agent / end user) , and (2) filter by "latest reply by end user", so the latest reply by the end user goes to the top. 

Currently it is only possible to group based on updater type, which it not working because I want to see who replied the last time, so if I update something without replying, that view will dissapear since I just did make an update. I don´t want to filter by "latest update by requester", as there can only be 1 requester. So if another end user replies the ticket, it doesn´t get updated. I don´t want to use "latest update" either since that includes my own updates.