Suggestions for my ultimate predator showdown before I make it?

How about a pack of Mapusaurus?

That'd make things interesting as Mapusaurus rosae is extremely large and if they hunted in groups that'd make them really dangerous.

Concur with the addition of Mapusaurus

I also have recently found out about a new species of Tyrannosaurus.  It has been dubbed Tyrannosaurus imperator.  With this only having a 16 year old to represent the species it is really large.  Being 13 feet tall, 51 feet long and weighing a whopping 13 tons he may have a great advantage here.  Should I add it?

It was not 13ft tall 51ft long or 13 tons in weight; T.imperator is synonymous with T.rex.

I looked into it and it is a distinct species.  The differences in the skull make it more like an over sized Tarbosaurus than a T. Rex.

^No, the specimen to which you are referring is UCMP 118742, aka the Peck's Rex. The reason it used to be estimated at fifty-one feet long was because they were stupid and used the bones of a f*cking sauropod. So now it's downsized to 12.2 meters.

Also, it's debatable whether S.morrocanus is the same genus as S.aegyptiacus or if it's an entirely new genus--Sigilmassasaurus brevicollis.

Oxalaia?