For years Tyrannosaurus rex has been the undisputed holder of the title biggest meat-eating dinosaur. But last year palaeontologists uncovered the remains of an animal that puts T-rex in its place. The aptly named Giganotosaurus, unearthed in the Patagonian desert. lived about 100 million years ago and was heavier, with slightly shorter legs, than the T-rex with a scissor-like jaw to tear its prey apart.
depending on how specific your answer needs to be the answer will be any one of the many bipedal saurid dinosaurs... in other words T Rex and its look alikes.
the elasmosaurids, though quite large as well, were actually marine reptiles and not dinosaurs at all so they will not count.