What Abby said is correct and the most natural for the context.
It would be used by natives.
Unpleasant better fits the scene and the incident.
Undesirable is ok but is used to describe effects or consequences etc.
not wanted or desirable because harmful, objectionable, or unpleasant.
not wanted, approved of, or popular:
it has a very small interchange with unpleasant in a dictionary but undesirable is more used like this
parents to child
"I wish you would move away from that undesirable neighbourhood"