tam crudeles erant ut plurimos Rutulos dormientes interficerent: in what way were Nisus and Euryalus cruel?

First identify the part of the sentence in which the answer is. This will be from 'ut' to 'interficerent', since the question 'in what way were Nisus and Euryalus cruel?' is practically a translation of 'tam' to 'erant'. We can see that the sentence includes a result clause from the introductory 'tam' and resulting 'ut'. Therefore, the answer lies from 'plurimos' to 'interficerent'. Always 'IVF' - identify verb first - 'interficerent' is the verb, the 3rd person plural imperfect active subjunctive. This is standard vocabulary, 'they killed'. Next identify the subject which we know to be Nisus and Euryalus from the context of the passage. Next, find the object, 'plurimos Rutolos dormientes'. Since they all agree with each other as masculine, accusative, plural we put them together and translate and get 'very many sleeping Rutulians'. So the answer for 2 marks is that they killed very many Rutulians while they were sleeping.