Halo: Every Covenant Species, Ranked From Weakest To Strongest

The roster of alien bad guys featured in the Halo universe ranges from ancient murder robots to evil meat mushrooms; however, the Covenant is the original cavalcade of interstellar enemies-of-humankind. Essentially, as a league of fanatical alien zealots, the Covenant is composed of several alien races united under a pseudo-religious doctrine that seeks to bring about the end of all sentient life in the universe, albeit unwittingly.