Human

From Wikitroid, the Metroid wiki

Humans are a weak species in combat standards that appear in the Metroid series. They don't seem to be any different from real-life humans except for their advanced technology, such as the cybernetic enhancements. As they did not evolve as a hunting or battling species, they require weapons for combat purposes. They play a large role in the Galactic Federation and helped create it as referenced in the Metroid manual. Samus Aran is a human and possibly the most powerful human in terms of battle capacity.

As demonstrated by Samus and PED Troopers, humans appear to be more resistant to the mental effects of Phazon exposure.