Last activity date w/ owner of last activity by accounts report

We have a number of reports on our OTBI Dashboards that looks at last activity by account by a few different categories. Recently we've felt that bringing in the name of the owner of the last activity would bring more insight. Whenever I try to do that though, the "Last Activity Date" field then lists last activity for that owner so accounts get duplicated on the report. We want to look at specifically who was the last person to log an activity, not see a list of all activity dates. How can I do that? Would it be best to