Velocirraptors!

YIKES!

In Velociraptor's case, size did not matter. Velociraptor was a small dinosaur (2m long and 20 kg), but a highly efficient killer. Groups of Velociraptor would have been a common sight in the ancient Nemegt Desert. They were light and athletic dinosaurs capable of running fast and jumping.

Velociraptor probably hunted in packs, like modern dogs, as this would have allowed them to tackle prey considerably larger than them. Thanks to the famous 'fighting dinosaurs' fossil we know that Velociraptor hunted the stocky Protoceratops, but may also have hunted other smaller dinosaurs such as Mononykus and Oviraptor as well as mammals, lizards and insects.
Younger Velociraptor probably raided the eggs and hatchlings of the many dinosaurs that used the Nemegt Desert as a nesting ground.
If we assume that the dinosaur behaved like modern pack hunting animals, Velociraptor hunting groups would have attacked by cornering its prey and then mounting a simultaneous attack until it died of exhaustion or blood-loss. One particularly effective attack technique would be to jump at its victim with its claws outstretched. It would then drag a specially sharpened foot claw down the prey's skin, inflicting terrible wounds. Repeating this several times would have severely weakened any prey, hastening its death.
In many respects Velociraptor was the ideal predator for the desert-like conditions found in the Nemegt. It was light, manoeuvrable and able to hunt and live on smaller animals. The average Mongolian dinosaur would probably have been more terrified of meeting a pack of Velociraptor than a giant predator like Tarbosaurus.

The Evidence

Velociraptor was first discovered in the 1920s. But few people had heard of it until the 1990s, when the release of Steven Spielberg's blockbuster movie Jurassic Park made the dinosaur a household name.
In life, Velociraptor was under a metre high. But what it lacked in size, it made up for with a deadly array of weapons. It had razor-sharp claws on its hands and feet including an enlarged second toe claw that could swivel round to inflict horrific ripping wounds on its prey. It also possessed a long snout and a mouth laden with rows of sharpened teeth. These features made Velociraptor a killing machine.
In fact, Velociraptor is one of the few dinosaurs which we can say for certain was a predator. This is thanks to an extraordinary fossil that was discovered in Mongolia in 1971 showing a Velociraptor locked in combat with a Protoceratops. The Velociraptor is raking at the Protoceratops belly with its hind feet whilst the Protoceratops has the Velociraptor's arm in its beak. It is assumed that the two animals were overwhelmed by a sand storm whilst in mid-battle.
That an animal as small as Velociraptor could have attacked a dinosaur so much bigger than it suggests that Velociraptor may have hunted in packs.
One further remarkable find from Mongolia shows the fossilised skeletons of two juvenile Velociraptor in the nest of another dinosaur called Oviraptor. The two Velociraptor might have been in the process of raiding the nest when they were smothered by the shifting sands of the Nemegt desert.