Hi,

First of all - never ask why someone hates the job. You'll fail the interview:)

The main objective is to have a good conversation and highlight your intellectual capacity and curiosity. Thus:

It is ok to ask:

• Questions that cause positive emotions and highlight consulting pros (e.g. Mck people)
• Questions on the topics you are excited about (e.g. data science)
• Non-business questions (e.g. team retreats)

It's not ok to ask:

• Questions that can cause negative emotions (e.g. work hours)
• Information you should learn before the interview (e.g. typical career path)
• Questions that may show that you are unfamiliar with consulting work (Like are you specialized in strategy or operations?)

Be prepared and good luck!