It was more of a major miscommunications that led to a toxic situation, both are equally at fault, and both didn't properly handle the situation correctly SPOILERS!!!!!!!! For those who haven't read the story:
From the Diego standpoint Kyrex was very much verbally abusive ,However From the Kyrex standpoint Diego was a stalker who kept harassing him and wouldn't leave him alone also kinda manipulative as kyrexs lost his job thanks to Diego's connection to Tai who is in turn linked to Lukas (Kyrex's employor). All of it is just so messy, as Jay said "Sometimes people just aren't meant to be together" Everyone shares fault