Dante

Dante is a manufactured shiny pokemon, though he wasn't shiny at birth. He was captured by a corrupt laboratory who changed him to be a different color, though he had a negative reaction to the injections and tests that where done on him. His attitude became erratic and he would also get more aggressive than he ever was before all of this. When Harmonia and her group where escaping the lab, they tried helping Dante out, but couldn't get through his cage in time. One of the squad members started to make fun of Dante before they left, and Dante was deeply saddened by this, thinking from the echoes of the lab that everyone was mocking him. Eventually, he got out as well, and vowed that if he ever found Harmonia again, she'd be finished. 

Much like Harmonia, Dante is only back due to a video I'm working on, so his story would be awkward without the inclusion of Minty. All that happened in the labs are still canon for both of them, though after that nothing is confirmed.