Which adult specimen ?

We have shockingly small adults; such as Chinly - Mud Butte Tyrannosaurus

I'll go Jack. It's been a while since I've seen Dinosaur Revolution, but isn't this the guy who had to be double teamed by Stumpy and his wife? I think he's got more feats than Bull

Bull is more muscular and robust, so a headbutt alongside Bull's close combat agility would likely shatter Jack's bones. His size get's retconed a lot, but apparently he's standing at 5 m tall, 40 ft long, and approx. 8 tonnes.

The T. rexes are the worst designs in Dinosaur Revolution. They might look cool, but they don't belong in a documentary.

Nothing to do with who wins in a fight, though.

I mean Bull went toe-to-toe with a JP3 Spino who broke the small plane in half technically.

^

And the fact he finished eating before the fight is even more impressive as eating before a fight can cause poor digestion, discomfort and slow timing.

@AFictionlover That's wrong assumption; it did not finished eating before going after the trapped JPIII People/Crew. Some of the carcasses parts were still on its mouth.

Ok yes he did not finished eating, but he WAS still eating and his snout was very bloody, so it must've been a long feast.