Nasty
Do you think your examiners would ask a harsh question at the viva? If you think yes, why?
If you think yes, what do you think it would be about?
And if you think yes, how likely do you really think it is?
I don’t think it’s common for candidates to worry about particularly nasty questions, but for candidates who do the worry is particularly nasty. If it’s on your mind, don’t wait to find out if your fears will come true at the viva.
Talk to someone. Talk to your supervisor. Review anything and everything related to the topic of the question.
Questions at the viva shouldn’t be nasty but if you’re worried, don’t wait: do something to help yourself.