"I really don't like the stock market. I wouldn't be a financial adviser for all the money in the world. I wouldn't want to be responsible for people losing their life savings because I picked the wrong stock or bond. It's too much pressure and like gambling, which just isn't worth it for me."

This is a variation of the old 'what are your weaknesses' question. The problem is that it asks for an example, so turning this into a positive 'I'm too detail-oriented' type of thing won't work. You have to be honest. You can't say that your ethics get in the way without them asking what would challenge them. Being honest with your interviewer is the best policy. I'd advise not saying that your least favorite task is what you're applying for. Saying you hate Auditing but you're applying for an auditing role would be a mistake.

Try to pick something that has nothing to do with what you're applying for.

"I really dislike taxes, which is why I'm applying for an auditing role. I'd never want to miss something due to my dislike of a task. With the various aspects of Accounting, it should be easy enough for me to avoid something I dislike."