"Unconditional" love or respect is often idealized or even expected, especially in communities of faith. But what is intended to be a beautiful picture of the love of God can contribute to abuse dynamics if it is not balanced with accountability. 
Those who have committed covenant-breaking behavior (abuse, adultery, abandonment, addictions) should be held accountable for their actions, if that can be done without compromising the safety and consent of their spouse. The same is true for toxic behavior in relationships other than marriage. Abuse will not stop by wishing it away or trying harder not make someone angry. It will continue until the abuser is stopped, either by an outside force or by being separated from the one they are abusing. 
Sometimes the best way we can love someone is to let them experience the consequences of their behavior. That can be so difficult to live out! As hard as it is for those in healthy relationships to understand, victims can have a lot of love, compassion, or admiration for those who are hurting them. (That's often how the offending person even has access to abuse.) They can also be dependent physically or financially. They want to extend forgiveness to fix the relationship, and they do so over and over and over again. Things may get better, at least, for a while. But if the root cause is never addressed, the toxic behavior is going to repeat, maybe in a different way but usually getting worse. 
Communities can have a hard time understanding how to respond to such situations. They want a quick fix to make it all better again, but they don't know what really happens between two people and often respond to the person "making a scene" rather than the person who caused the damage. But it is normal human behavior to have strong emotions when we are wounded. We were designed that way to have the motivation to leave dangerous situations. How many wrongs have been committed by stifling the voice yelling, "Something is very wrong here!"?
It is tempting to believe promises to never hurt them again or to try to do better. But words are easy. The only way to see a real difference is to pay attention to actions, and not just for a day or two. A truly repentant person will demonstrate over time that they are not continuing the same toxic behaviors. They will patiently and respectfully rebuild the relationship they ruined, showing compassion and understanding to the person they hurt.
The proper response will vary for each situation, but there are some commonalities. Always begin with prayer for discernment and compassion. Any burden of relationship repair should ALWAYS ONLY be on the one who damaged it. And the wounded person should be given the grace to respond as they need to, the space to feel safe again, the time to heal, and the support to rebuild what has been taken from them.