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[MCU] what is the difference and relationship between the Kree, the Chintari, And The Other?

i just watched through the whole MCU (yes, even Hulk) and was confused about the alien species that appear.
First, the Chintari invade earth under the direction of Loki, and supplied by The Other (Thanos' henchman).  How did The Other get the Chintari under his control? 
Next, in Agents of Shield we see project Tahiti used Kree blood. Originally, I thought the Kree were part of the invasion of New York, and that's where Shield got the Kree body, but that doesn't match the timeline.
Then in Guardians of the Galaxy we see Ronan, a flesh and blood Kree. He too is working for Thanos and The Other. 
I guess before I re watched all the movies, I thought the Kree and the Chintari were the same species. After re watching, I know they are different, but I'm confused as to their history, motivation, and connection. It seems they are both races being used by Thanos to his end game of the Infinity Gauntlet, but I don't know who they are or why they would agree to work for Thanos.
gpt
I'll have to break the fourth wall here, mainly because the MCU hasn't really built much of a fourth wall yet in regards to these species.

The Other is Thanos' personal servant. He bears a resemblance to 616's Corvus Glaive, but where Glaive was Thanos' right hand man and chief assassin, The Other doesn't have much back story. 
His species doesn't really matter because the universe is a big place. He was brought in more to scale how powerful the characters are. 
Loki, who is a badass who takes on the Avengers, is scared of The Other. Ronan The Accuser kills The Other with a casual backhand. Ronan is scared of Thanos. There's always a bigger fish.

The Kree are a major player in terms of galactic empires. As a whole they tend to be a more martial, antagonistic people. However their willingness to sign a peace treaty with the Nova Corps is sign enough that they also value diplomacy to a degree. They're analogous to any of the major players in our world in that regard. It should be noted that Ronan the Accuser is not indicative of your everyday Kree. He's a religious fanatic out on a crusade. He's the larger galaxy's version of Osama bin Laden. 

In the past more warlike sections of the Kree empire developed a bioweapon known as the Terrigen crystals/mists which induced in certain lower species, like humans, a process known as Terrigenesis. Basically taking barbarians, giving them superpowers and then using them as living hand grenades. In more recent times the ruling body of the Kree has determined that giving people superpowers is a bad idea and brought the practice to a halt. The Kree that T.A.H.I.T.I was based on is one that came to Earth in the past to make humans into bioweapons, Vin-Tak came here to stop him. Politics. 

The Kree are not working with Thanos. Ronan was working with Thanos. Ronan was fighting an ideological war and worked for Thanos so that Thanos would in turn lend him his might. Ronan was a rogue element among the Kree. 

The Chitauri in MCU are different (comic Chitauri are way different). They're not really like anything in the comics. They kind of look like a mix between the Skrulls and the Phalanx. They were brought in because Joss Whedon needed an alien army that could be brought in without any heavy backstory and the comic baggage that comes with it. 

In regards to an in-universe answer. The Chitauri are an alien race that works for Thanos. Thanos is an intergalactic warlord with phenomenal power and innumerable armies - the Chitauri are one of his forces. 

Thanos doesn't like to go hands on directly. He works through agents. Thanos' goal is to acquire the infinity stones. So that's pretty much the price for getting Thanos to help. Ronan wanted the Nova Corps crushed, the price is the inifinity stone on Morag. Loki wanted to conquer Earth. Earth has an infinity stone (the Tesseract), so Thanos lent Loki some goons.