which word does the attributive clause modify?

the absence of strife between the generations that was so characteristic of such societies

Does the attributive clause modify the word "absence" or the word "strife" ?

I guess it modifies "the abscence of strife". That´s one unit. However, if you really want to pick either of the two, then it`s definitely "the abscence" that is modified.

Without seeing the whole context, it's hard to tell, but I agree, it's probably "absence".