Need the Last Comment, Script Runner Fields can help.
Create a custom script Script Runner Field and use this code
import com.atlassian.jira.component.ComponentAccessor
def commentManager = ComponentAccessor.getCommentManager()
def comment = commentManager.getLastComment(issue)
// check to see if comments exist - return comment body if so
if (comment != null) {
return comment.body
}
return null
It returns the last comment and can be used as a field in dashboards.
I found this in an older JIRA community post, but don't remember where exactly so I can't give proper credit -thank you for who ever created this.