How to toughen up against hostile students as a TA? I did not have a good experience when I TA'ed the first time. I faced a hostile student who refused to accept that he was wrong and didn't give me a good reason why he should deserve more marks. He showed a propensity for violence, shouted at me loudly, punched the table and gave me an extremely evil look. I was very afraid and shocked then. 

I know I should have stopped the meeting and called the security. But I was at a loss then. I don't like that I was so easily frightened by a bad student. Though I haven't met such a student later, one never knows when the next time will be. Can anyone advise how to become tougher when facing such "evil" badly behaving students?
Your responsibilities as a TA do not include being verbally abused or physically threatened by irate students.  At the first indication of abusive behavior, immediately stop arguing or doing anything else that might further provoke him.  Instead, in as calm a voice as you can muster, inform the student that you understand his concern but that you don't have authority to grant his request but that the course instructor does and that you propose to set up a meeting for him with the instructor.  Immediately afterward, send email to the instructor explaining the problem and let the instructor deal with it.  

If it's already gone past that point, and he's pounding the table, shouting and exhibiting threatening behavior, get away from him as quickly as possible.  Tell him you need to go to bathroom or whatever it takes to get away without being followed.  Do not return. Call campus security.