This won't just be a lame "what I think its stats should be." This will be exploring the probable relationship between Tyrannosaurus and its prey and competition in The Isle. Some animals will be easier than others, since some (or their close relatives) lived with Tyrannosaurus (or its relatives). Others will be much more difficult, living in environments completely separated from Tyrannosaurus' grasp. However, I can still present my thoughts about this in the most accurate way I can. This will both explore from a solely realistic view, as well as a more balance-centric view. When possible, I will look at T. rex's hunting habits more than it or its opponents physical traits, since it gives clues as to how significantly of a threat Tyrannosaurus viewed each prey item, rather than what we simply think or predict what would occur based on physical traits or strength, something which can neither be known completely for certain, nor perfectly compared.
Probably the easiest creature on this list, the famous Triceratops is the well known prey of T. rex. People generally think it ought to be an even 50/50 fight. But ask yourself this: "why would T. rex hunt Triceratops on what appears to be fairly regular basis if it had a 50% chance of dying every single time?" It wouldn't. We have found enough fossils of T. rex bite marks on Triceratops (particularly the frill) to show it hunted them frequently. However, we have also found, among these remains, wounded Triceratops that lived at least long enough to heal the wound, showing Triceratops could infact fend off T. rex attacks (though it didn't necessarily kill them every time). Additionally, there's the fact that T. rex even bothered to hunt Edmontosaurus. The reason this is significant is that Edmontosaurus was considerably faster than Triceratops, meaning that T. rex would have to put far more time and energy into hunting it compared to Triceratops. Unless Triceratops posed at least a mild threat to Tyrannosaurus' well being, it would certainly have hunted them much more frequently compared to other herbivores in the environment, contrasting what we find. Noting this, we should now come back to the fact that Tyrannosaurus generally attacked Triceratops on the frill. Taking a few measurements, and simply lining up Tyrannosaurus' mouth with Triceratops' frill in the game, to prove it's applicable to the somewhat skewed sizes, this actually puts the placement of Triceratops' horns, even its nose horn, in just the right place to hit T. rex in the throat. Recent findings even show that Triceratops' brow horns curved upwards, making them even more efficient at impaling T. rex's throat. However, given that T. rex had a larger, more muscular neck than Triceratops, it would likely be able to overpower its prey without significant injury, at least, most of the time. This helps indicate as to why this relationship appears to have been the case.
This is largely a PvP game currently though, and will probably keep a large portion of that PvP nature for the rest of its existence. As such, Triceratops should be able to defend itself from T. rex attacks more effeciently than in real life. Afterall, what's the fun in playing as a creature if you just get killed constantly? Once locational damage is in, this will probably be the case. Triceratops will be able to easily hit Tyrannosaurus in the neck and underbelly, whilst Tyrannosaurus will only be able to hit it on the frill and moderately armoured back. T. rex should still have a fairly significant advantage though, at least in my opinion, to maintain at least some realism.
Now this one shouldn't take as long. Ankylosaurus' armour was thick and tough. Probably not enough so to fully protect from a Tyrannosaurus bite (T. rex could bite for over 6 tonnes of force afterall), but certainly enough to help it in combat. Additionally, and, perhaps more importantly, Ankylosaurus' armour had very little curve to it, and was too low to the ground for T. rex to bite from the side. T. rex may as well have tried to bite a wall. The shape of Ankylosaurus' armour would have made it impossible for Tyrannosaurus to attack at it with anything more than the weakest of bite, and the toughness of the armour could take over from there. Tyrannosaurus could not have stepped on Ankylosaurus' back either. The fact that T. rex's legs were about half way back on its body would put it in striking distance for several seconds before being on top of its desired prey item. Regardless, I don't think many (if any) attack marks from T. rex have been found on Ankylosaurus.
In game, Ankylosaurus should certainly be the last prey item you would pick. Though I would argue to make it less-than-invincible so as to not make it completely unfair. The club should also do somewhat low damage so as to give it some kind of short coming. Additionally, it would be (as it is currently) slow and annoying play as, despite its strength, to make it less desirable (we can't have nearly invincible tanks running around everywhere).
Now we move to a more tricky one. I would talk more about Anatosaurus (Edmontosaurus annectens), but there is a significant lack of fossils for "super" adults making it difficult to really tell how often Tyrannosaurus hunted them. The closest thing to T. rex in Shantungosaurus' environment was Zhuchengtyrannus. How common or rare fossils of those are is actually irrelevant to what I am talking about in this section. All we need to know is that Zhuchengtyrannus approached T. rex in size. It didn't quite equal Tyrannosaurus, but was still a very large and powerful predator.
Now to the heart of the matter. If Zhuchengtyrannus hunted Shantungosaurus as a typical food source, we would expect 15+ meter Shantungosaurus to be incredibly rare, as we see with the considerably smaller Anatosaurus (estimated to reach a maximum of 15 meters, based only on weak material. Most adults died by the maximum size of 12-13 meters, many died by only 9 meters in length), and yet, nearly half of our specimens of Shantungosaurus actually top 16 meters (with one reaching nearly 19 meters), with none showing obvious bite marks. This would imply that Zhuchengtyrannus could not hunt Shantungosaurus past a certain size (or at least typically chose not to due to high risk). Tyrannosaurus, being noticeably larger than its relative, and being known to hunt reasonably large hadrosaurs already, likely could hunt them to a considerably larger scale, but given the Shantungosaurus in game is over 15 meters long, larger than any hadrosaur known to live is T. rex's environment, and may have been in more fit condition than even the really large (and really rare) ones in T. rex's environment (since it's more average for its species, it would imply to some extent that it would be somewhat younger and thus healthier), it would likely be a battle too risky for T. rex to realistically engage in unless desparate, which, as mentioned in my earlier Triceratops section, would translate to roughly 50/50, or at least uncomfortably close to it for T. rex to regularly engage in.
In game, T. rex should be able to kill Shantungosaurus with relative ease if it ambushes from behind, but it should otherwise it should be a fight too risky to take unless desparate. The new stamina system should prevent Shantungosaurus from chasing down T. rex, as they did in the past, and since the fight would be roughly even, they wouldn't want to risk it either. Additionally, Shantungosaurus' somewhat "Jack-of-all-trades" type generalized design would make it prey to other apex predators as well, making its risk of running into something that might hunt it considerably higher than other herbivores.
Therizinosaurus did share its environment with Tarbosaurus, a close relative of T. rex. Not as large or heavily built as Tyrannosaurus, but still a worthy opponent, meaning it would probably have decent defense against it. A similar variety of herbivores existed in the "Turkey's" environment as compared to Triceratops, though mostly on a somewhat smaller scale. The comparison is probably pretty similar then, though Therizinosaurus proabably utilized its speed moreso. Additionally, Tarbosaurus was still smaller than T. rex.
Therizinosaurus ought to be able to somewhat defend itself from T. rex, but should generally run away since T. rex would be stronger but slower than Tarbosaurus.
One of the common arguments for Stegosaurus being very weak is that it only had to deal with Allosaurus. However, this not actually true. Both Torvosaurus and Saurophaganax (possibly synonymous with Allosaurus) lived in Stegosaurus' environments, and both reached lengths of around 11 meters, and weighed in at around 4-5 tonnes, comparable with Tarbosaurus and even nearly as large as Acrocanthosaurus. Allosaurus have been found with injuries from Stegosaurus, showing they did try to hunt them, at least on occasion, but given both of the larger predators mentioned above did infact live in Stegosaurus' environment, it would at least be remotely equipped to handle apex predators, such as T. rex. Would it be enough to really threaten the apexes? No, probably not, but it should at least be strong enough to work as a deterent (and on a side note, I would enjoy a feature that adds more risk to hunting something even if you can kill it, such as minor infections).
Stegosaurus should be the weaker but more manageable 'apex' herbivore, requiring less food to funtion, giving it a less "lawn mower" playstyle. Additionally, once humans are added, it would likely be less of a target than other high tier creatures.
Due to the low number of documented real-life encounters between apex predators, there really is no choice but to compare physical traits.
What is there really to say? Acrocanthosaurus is smaller and less adapted to fighting with creatures its size and build than Tyrannosaurus. Given that Acrocanthosaurus isn't even technically an apex, Tyrannosaurus, in terms of a brawl, should have an easy victory.
Similar to Acrocanthosaurus. But given that Giganotosaurus is larger and is actually an apex, it should be able to do enough bleed damage to act as a deterent for T. rex, even though T. rex would typically win in a fight, for a few reasons.
1) T. rex was more muscular and likely out-weighed Giganotosaurus
2) Giganotosaurus was adapted to using speed and bleed to take down prey much larger and much slower than it, whereas T. rex was adapted to brawl with other comparably-sized, armoured, muscular animals.
Given that this creature is pretty much only in the game because Dondi "want[s his] JP Spino," (that's actually what he said) I think it's safe to say that the land Spinosaurus should be able to rival T. rex in a fight. Given that its sole purpose in the game is to directly rival Tyrannosaurus, it should be roughly 50/50 (which it would be with some minor adjustments to the current wonkiness of Spinosaurus' bite).
Unlike its terrestrial counterpart, this Spinosaurus is by no means intended to rival Tyrannosaurus, or any large predator for that matter. It simply hunts fish unbothered by the other apexes. This Spinosaurus shouldn't even approach, let alone fight, a T. rex.