Games Radar created a listing of the most superior races in games and they featured the Zerg (I would have chosen Protoss myself but I'm glad that they decided to include Starcraft). The Zerg were put as one of the most aggressive races and were rated as only slightly less "invincibly powerful" than the dinosaurs.
Race: Zerg
Evidence and source material: Starcraft, Starcraft II
Why they’re superior: Zerg are an alien race that travels the universe looking for species with powerful genetic characteristics they can incorporate into members of their own race to become better at killing. When they can’t find those particular traits, they work on burrowing, flying and reproducing themselves in an assortment of colors.
They’ve even acquired the ability to travel through the deep vacuum of space… naked. Humans look ridiculous naked and have to use something like this for intergalactic travel:
The downside: Zerg thrive and rely on being able to set up bases on living flooring known as Creep. It’s purple-brown and probably gooey. As humans, we prefer the comfort of asphalt and shag carpet.
Will they replace us? Unfortunately, the universe just isn’t big enough for more than one species, so conflict with the Zerg is inevitable. The best way to fight them is to put on a powered combat suit, load-up on more space marine-adrenalin shots than the human body can handle and weld your finger armor to the trigger of your futuristic assault rifle. Odds are, though, you’ll still end up being an embarrassingly easy meal for something called a Zergling - the only “ling” in the universe that can eat your face off.