In my mind it comes down to a question of what we have control over.
If you intend something good, but chance and circumstance destroy your good intentions, then I value the intention more than the consequence. Mistakes happen, and I can absolutely relate to that. If the circumstance doesn't represent the true nature of the intention - the person meant to come visit you when you were sick, but their car was totaled, or they had depression and couldn't leave the house, or they genuinely got confused and forgot, but regret forgetting, etc. then I see that as not even needing forgiveness. It is the thought that counts.
If they have control over the outcome, it goes as planned, and it causes harm, pain, and destruction, then I cease to see the value of the 'good' intention because people have a responsibility to learn and revise their world view to be kinder. If the intention is a justification for causing harm and destroying lives, then I look to the consequence as a way to challenge the notion of someone's intention. At that point 'good intentions' are just backwards reasoning to justify what is clearly an expression of anger, entitlement, cruelty.