While Drax isn't going to be attending any interpretive ballets any time soon, he's a solid guy in a fight. It's entirely possible that some things go over his head, reflexes aside, but there's a lot to be said for his durability, loyalty, and master of weaponry. Formerly an intergalactic criminal, he's now one of the Guardians' core members despite an uneasy start.
Groot is arguably the Guardian with both the most limited audible vocabulary and the biggest heart. He's teamed up with Rocket for a long time, now, following him through several adventures before the two merged paths with the other Guardians. The tree-like alien sacrificed himself to save his teammates during the battle of Xandar, but his stage of regeneration is up to the player.
On the other hand, despite seemingly spare with words himself, Kraglin isn't known for his tenderness. Serving as Yondu Udonta's first mate in the Ravagers, he's also joined the Guardians in several adventures, though his loyalty remains primarily with Yondu. He and Quill have had their rivalries over the years, but the latter considers their relationship to be on neutral, if not friendly, terms.
It's probably a good thing that he hasn't often crossed paths with the young empath called Mantis. After bonding with Drax, she cared for and allied with the Guardians, and accompanied them across universes as their friend and teammate. Despite her naivety and isolated childhood, she is intelligent, and considered a valued associate by at least a few of the Guardians.
However, few of them would be sad to be rid of Nebula. The other adopted daughter of Thanos fought against her sister before deserting Thanos, which resulted in her capture, and containment by the Guardians. Once she escaped from them, the cyborg assassin later fought for and against them several times before coming to an agreement with her sister. The last they saw of her, she went off on her own, claiming she was on a revenge mission against her adoptive father.
An annoying little trash panda with a particular proclivity for pyrotechnics, Rocket is a genetically enhanced Halfworlder, whose years of abuse and repetitive genetic rewrite caused him to develop a vain and chaotic personality. His best friend and partner, Groot, worked as a bounty hunter with him until the two joined the Guardians of the Galaxy. Despite his soft fur, he's a tough being, who seems to care more for his weapons than his teammates sometimes.
There's little question where Yondu's affections lie. The Centaurian is a leader of a key faction of the Ravagers, and adoptive father to Peter Quill. Sold to the Kree empire as a slave by his parents as a child, he spent two decades fighting on their behalf before being rescued and made a Ravager leader. Despite jokingly threatening Quill with cannibalism, something the boy took to heart, the two developed a close relationship despite Yondu's efforts at never showing him affection. Whether cinematic canon is modified or ignored is up to the player.