Frustration and anger from travellers. Those who are in a rush, or missed connections, or otherwise emotionally charged because something else is putting them under pressure.
Aggressive and potentially violent people who have lost emotional control, sometimes because their expectation of your service is unrealistic and sometimes because the service has let them down.
Unpredictable people. perhaps people with mental health issues, or those affected by alcohol or other substances, or both.
Vulnerable people. Again some people with mental health issues, maybe the young, the elderly, or confused people. It could be someone with learning disability.
Workplace conflict which develops because of a misunderstanding or miscommunication or something which is outside of your control or theirs.
Anti- social or disruptive behaviour, such as swearing, goading, jostling, queue jumping, rule breaking, adverse gang and group activity.
Criminal behaviour. This could include non payment for services you have given them, fare dodging, theft, robbery, or assault.