Answer:
The thing that should be avoided during an interview is speaking badly about others.
Explanation:
There are several reasons why you shouldn't talk badly about other during an interview, first of all, it is not professional if you are gonna talk about your former job and co-workers you'll talk about the one you are trying to get as soon as you leave. Another reason is that it doesn't make you look like a trustworthy person which is one of the principal characteristics employers look for in candidates.