I might just give it to Allosaurus out of my bias towards the dinosaurs from the Jurassic, but I won't for now. I'm not sure if a T-Rex could snap the neck of Allosaurus, but it could certainly choke it to death with it's bite, yet Allosaurus certainly wouldn't cooperate with that, and I can imagine Allosaurus lying on it's back and aggressively swinging it's arms to keep the T-Rex away from it's neck(Slashes to the gut are not beneficial to the survival after the fight, and if both die, nobody wins). If two would keep their distance in a fight, Allosaurus could use it's momentum to kill a Tyranno, but if both would come to grappling, it's more complicated.

However, a couple good pecks and slashes could end up as crippling as a T-rex bite if the Allosaurus could land them(it certainly could). Allosaurus is technically 70 000 000 years behind T-Rex in evolution and knowing the agility of T-Rex that is combined with it's stronger bite, it could still very well defeat an allosaurus even at the same size. I'm not ridiculing T-Rex arms, they were pretty strong and not that much smaller when compared to Carcharodontosaurus(I could laugh at Abeliasaurid arms tho, for joke's sake), but Allosaurus really relied on it's arms a lot more than T-Rex. Allosaurus most certainly had a weaker bite force than the T-Rex, but it's strong neck and sturdy robust skull suggest that it could probably perform a very brutal version of pecking, as well as it could use it's long claws by violently flapping it's hands. T-Rex skulls have bite marks which indicates that they did fight quite violently, while Allosaurus remains are found with many healed wounds, including the one where Allosaurus recieved a thagomizer to the back and possibly walked it off. 8:01 PM - Oct 27A very interesting topic indeed, as both dinosaurs are known to be formidable hunters and what's most important, active fighters.

Allosaurus vs t rex