What is the ruling on divorcing a wife six times in one sitting, knowing that she had been divorced once before and then again, and that the husband was in a state of anger?

Divorce pronounced during menstruation is effective according to the majority of scholars, even though it is forbidden to initiate it. Therefore, the first pronouncement of divorce is valid. If by "resuming" you mean taking her back (restitution) before the expiry of her 'iddah, and then divorcing her a second time, and you did not take her back, and then you divorced her a third time with six pronouncements, then she is forbidden to you and will not become lawful for you again until she marries another man and he consummates the marriage in a valid union. No expiation is sufficient in such a matter. This is the view of the majority of scholars and is held by the four madhhabs. As for the conditional divorce, it is now without effect, because the woman has already been divorced from you and has become irrevocably separated (bainunah kubra).