Guardians of the Galaxy was a big hit and it has got me excited about the Marvel cosmic universe, so I decided to document some of my favorite aliens that we may see in the upcoming movies. Lets check them out!
Marvel has a thing for creating nuanced cultures and characters, so no alien race can really be pegged as good or evil (though some come really close). They all butt heads, but at the time for seemingly good reasons.
Asgardians are a race of creatures similar to humans with technology so advanced it appears magical to us. Asgardians have a much longer life span than humans (either immortal or several hundreds of years, depending on the comic) and are considerably stronger and much more durable than Earthlings. They have ventured onto Earth many times in our history, more recently creating our Norse mythology. Heroes Thor, Sif, and Angela are Asgardians. Unlike many of the alien species, the Asgardians seem largely content to control their own realms and not seek conquest in the rest of the universe (sounds like this wasn't the case in the past, though).
The Badoon are one of the older races in our galaxy, controlling about a third of the Milky Way within their empire. They look like reptilian apes and are aggressively trying to expand across the galaxy, so they are occasionally a foe of Earth. They have faster than light travel technology as well as cloaking abilities, but they usually aren't any physically more powerful than humans. They also can create "Zom soldiers" which are the dead bodies of fallen enemies reanimated by cybernetic technology. Male and female Badoon live in separate societies. At one time, the two genders were at war, but the males ultimately ended up the winners and imprisoned the females. They formed two parallel societies, the men expanding outwards in their quest to expand the empire, the women looking inward and becoming pacifistic. They meet when they need to meet their mating urges. In the year 3000 the Badoon will conquer Earth and enslave Humanity. The Brotherhood of the Badoon would make an excellent enemy for a movie but unfortunately their movie rights are owned by Fox and not Marvel, so they may end up in a Fantastic Four film but not Avengers or GotG.
The Brood are a race of insect-like aliens with both an exo and endo-skeleton and huge teeth. They look a bit like Xenomorphs from the Alien franchise. Brood share a hive mind, so the experiences of one Brood are shared with the others. As such they don't see themselves as individuals and don't typically have names (save for queens and special outcasts, like Hulk's ally "No-Name.") They are all female, and breed by implanting eggs into other creatures, killing the host as the eggs mature. The Brood are very deadly, being large with powerful teeth and claws, and a sting that can kill or paralyze victims (as well as implanting eggs). They are sadistic and cruel, though there are a couple compassionate outliers. They have fantastic technology and cruise the galaxy in living whale-like space craft, eating tunnels through the giant animal's flesh like parasites until the animal dies.
The Kree are a race of militaristic aliens that look a lot like humans. The original Kree were blue skinned, but they activated a cursed artifact that ended Kree evolution, so they bred with humans trying to keep their species thriving and genetically diverse. The resulting offspring had all the human skin tones as well as blue hues, though blue Kree are still the highest "race" in Kree society (though the minority). Korath and Ronan from the Guardians of the Galaxy movie are both Kree, as well as the corpse in the Guest House in Agents of SHIELD. The Kree follow and worship the Supreme Intelligence, which is an AI that houses the biological minds of the greatest Kree thinkers. Poets, generals, philosophers, all their organic brains are plugged into the Supreme Intelligence which guides the Kree people. The Kree themselves are a good bit stronger than Humans, and exceptional Kree have super powers like Human mutants.
Millions of years ago during a war between the Kree and the Skrull, Kree military forces established a base on Uranus and discovered primitive humans on nearby Earth. The Kree experimented with humans there in order to jump start Kree evolutionary stagnation and to create a super powered people to use against their Skrull enemies. After the base was abandoned, these human test subjects would become the super powered tribe, the Inhumans.
The Shi'ar are humanoids evolved from avian creatures that control one of the most powerful empires in the Marvel universe. The Shi'ar Empire spans across several galaxies and comprises many different alien races. The Shi'ar themselves appear as humans with feathers instead of hair. They are much stronger than humans though though have hollow bones, and their people don't exhibit super powers. They have many advanced technologies like holograms and warp gates for instantaneous travel. While individually and culturally very aggressive, the Shi'ar Empire (ruled by a council) often takes up a peace keeping role in the cosmos. I could be wrong but I think they are one of the few empires that hasn't tried to fuck Earth yet.
The Skrull are one of the coolest Marvel species ever. They are a reptilian people tampered with by the ancient Celestials (like humans) that developed shape shifting abilities. One of the first species to develop space travel, they would fly to an inhabited planet, disguise themselves as the dominant life form, and share technological secrets. They would do this in order to add to their number of trade partners throughout the galaxy. They were responsible for giving advanced technology to the Kree, who promptly spread across the galaxy and attacked the Skrull home world. The Skrull had to become more warlike in order to defend themselves, and they totally reshaped their society into the warrior culture that exists today. Some Skrull today not only have the power to change their form, but mimic the super powers of Earth's heroes. Most famously among these is Super Skrull, who has all the powers of the Fantastic Four at his disposal. They are one of the greatest villains in the Marvel universe so it hurts my heart that they are currently owned by Fox, and not Marvel.
These are some of the big hitters, but if I missed your favorite aliens please note them in the comments. Also, if I messed up the descriptions please let me know I am full of shit too. Which aliens would you like to see in future Avengers or Guardians movies?