Right. Now let me logically create the playing field.
The T-Rex/Raptor was genetically engineered to be the ultimate hunter.
The only way a Predator could defeat it is if it was a Predator who was an ultimate hunter. Now let's go and search for that said hunter. Which is Scarface.
A Predator would not use his weaponry Apex. Because the combatant is a Dinosaur who is one. Not many. A predator only uses his cannon when he is out numbered. But it's a fair fight so the predator would use his gauntlets. Spear and so on.
A Predator would not use a cannon. If he had used a cannon it would defeat the purpose of a fair fight. The dinosaur is unarmed. He would have to challenge the beast with his own claw.
The Predator would be equipped with a grappling hook, similar to the one in Lost Planet 2. In order to even clash with this Apex predator, the hunter would have to aid for the ankle and eyes. Considering the Predator is invisible it would have an edge. However, the dinosaur also has form of camouflage and heat sensors would not pick it up. So the predator would have to use one of his artificial sensors. Knowing scarface he would sacrifice one deadly attack from the beast to take it out. Both mortally wounded Scarface would finish the Dinosaur. However, if it was any normal predator it would win simple as.
Scarface would be the only Predator strong and skilful enough to defeat the dinosaur without weaponry.