If you think about it, being nice is another way of saying that you're flexible to another person's needs. You take them into account and deal with them accordingly. That isn't a weakness at all!
Is kindness a strength or weakness?
As Armitage explains: “Kindness is not typically associated with strength but, in actual fact, sometimes it's the strongest people who are able to be the kindest; they don't feel the need to use defences, or put up barriers to protect themselves, and can therefore offer genuine kindness because they feel safe and ...
Why is kindness a weakness?
Why kindness in the context of the workplace is often taken for weakness. As if being kind, means being soft and indecisive. As if being kind means you are not able to deliver the best work. As if helping others must mean they are not capable enough.