We all know that non-virtuous actions creates negative karma. However, negative karma is not only accrued via explicit non-virtuous or negative actions. If you carry yourself in a way that makes people lose faith in Dharma or if you act in a way that makes others have negative thoughts, you will also created negative karma. The basis of negative karma here is harm inflicted on others.
Explicit non-virtuous action is self-explanatory. However, harm inflicted on others by causing them to have negative thoughts or wrong view is more subtle.
Also if we have negative propensity for eg laziness but for the time being does not harm others, it will also accumulate negative karma because if we continue to be lazy, we are reinforcing the negative propensity in ourselves and eventually when conditions are right, it may cause harm to others. For the time being, negative karma is accumulated because we are causing harm to ourselves by reinforcing our propensity for laziness.
Therefore, negative karma is created on the basis of harm inflicted on others and ourselves. How many of us realise that we can create negative karma without committing explicit negative actions?