Here's some info about the Guardians' corrupted versions in my AU:
Cubic: They can be extremely grumpy sometimes, but they're not humorless, telling them any kind of joke can trigger a good reaction if you put some real effort into it. They have kind of a green thumb, so much so, that when possible, they'll still go outside of Blixer's tower to take care of plants and make sure they don't die from the corruption. They find Cube's softness to be unreasonable, Rubi's whimsy to be nonsensical, and Hethagon to be really dense regarding her crush on Cube, the only guardian they don't have any strong opinions towards is Sheba, because she's relatively normal and responsible, unlike the others. Even though they think Hethagon is dense, they still prefer her over Hexatrix's obsessive personality.
Hexatrix: Hexa is extremely obsessive, twisting Hethagon's crush on Cube into obsession, which is what drives her to chase them down and corrupt them into Cubic. Blixer finds this obsession funny, so he always sets her on the same missions as Cubic, but not entirely on malicious intent, more so because Hexatrix does better on missions when Cubic is involved, after all, they are the one corrupt she does literally everything for, so they serve as motivation for her to do better, and it works (Hexa and Cubic have a Pucca & Garu sort of relationship, except Cubic doesn't avoid her like a plague, and she's not trying to kiss them). She is still best friends with Rubix! So much so, that when they battle together, they support each other! (Which is pretty big considering that if Cubic is involved, she'll charge in all by herself).
Rubix: If her vuvuzela wasn't enough of a nuisance before, now it's even worse! Unlike Rubi, however, she doesn't use it outside of battle. Her and Hexa are still great friends, just like their uncorrupt selves, she's also probably the only other person that Hexa works really well with, aside from Cubic. Sometimes, Rubix pulls Hexa along with her into missions, only letting Blixer know about it once they're already doing their jobs. Rubix is still a loyal best friend, just- less whimsical and more... rebellious, I suppose.
Sheba doesn't have a corrupted version, but if she did, she'd probably be either: very diligent, cold and calculated, or, to contrast her uncorrupt self's personality, more lazy and careless.
But in general, none of them are heartless, they're just doing what they're told.
