Romulans
I wish we had more focus on the Romulans. They were always this big threat but never were really the main villain.
In Enterprise, they could have transitioned to a Romulan war. If even be happy with a new series about it.
Season 5 of Enterprise was planned to be the Romulan war unfortunately they never got the chance to make it. Now thanks to Jar Jar Abrahms getting rid of Romulus we’ve probably seen as much of them as we’re going to at this point.