It’s easy to assume that unkind is the opposite of kind.
But that’s not the case.
While one person’s behavior can be considered kind, someone else’s with the same behavior might be considered unkind.
One person’s behavior may be intended as kind but received as unkind.
There is also the definition of what kind or unkind is.
For some, being kind means giving what the other wants. For others, being kind means being clear about what can be given and what can’t. And there will be other definitions of what kind can relate to in different situations.
In general, however, being kind and unkind will have a long-lasting impact. People do remember. Being kind has a short cost on the person being kind, as that person needs to determine how to be kind, even in a situation where this might not be easy.
Being unkind usually doesn’t have a visible short-term cost. However, in the long term, the cost is the risk of the unkindness being returned by the person. For example, by not being willing to make the effort to be kind.
It’s the outcome or the impact of being kind and unkind that may be opposite. The behavior itself is just different.