Congenital hypoalgesia on rex
Im not sure that it works but prime trike and prime deino are bigger than rex mass wise(same for adult trike and frail elder deino), same will be true for spinosaurus(plus camarasaurus and shantungosaurus, if well live to see its release). So basically bleed resist + fracture resist + congenital and the only 3 dinos that can kill rex rn (stego, trike, other rex) will have a harder time in doing that. What do you think?