Malakye's first relationship was with Adelard, and for the most part it was sweet and healthy. But it ended because Adelard never accepted help with his mental issues, and he hardly communicated with Malakye. So, when it became too much, Malakye left. Because he's not responsible for the happiness of someone who can't accept help, and it was a hard pill he had to swallow.
His second relationship, the shortest one, was unfortunately with a cop. He doesn't even remember how it happened or why, but he somehow loved Daniel. That ended on a worse episode than with Adelard. It ended with Malakye bruised, cold, aching, and losing all trust in love and life.
His third and longest-lasting relationship, years later, was with Kerys. She was always patient with him, and was honest and communicated and apologised whenever she upset him. That relationship didn't end.
Adelard, while he acted irrationally, never physically harmed or threatened Malakye. Despite his flaws, he was, for the most part, a good person. He was still always a good friend to Malakye. They just didn't work out in a relationship, and Adelard was raised to keep all his struggles inside. It just overflowed, and Malakye was there when it happened.
Daniel was never a good person. He knew he was hurting Malakye, he knew it was wrong, and he relished in having that control over someone. Nothing can redeem him, not even after death.
Kerys was good to him. She obviously has her own flaws, but she's good to Malakye. He's never felt so comfortable and loved. She may have been a dangerous assassin back in her original universe, and rarely innocent people would get caught in the crossfire - which struck guilt deep within her - but with Kerys, heaven and hell were just words to Malakye.