What tense do I need to use with the word before
They truly believe that the benefits we obtained are nothing compared with the damage we caused/had caused before.
Either is possible. "Before" makes the sequence clear, so the past perfect is not necessary, but it is used in written language.
The thing that you have to learn about tenses in English is that, a lot of the time, there's no single 'right' tense to use. There's usually one or more that are wrong, but it leaves several that correctly and appropriately convey the meaning you intend.
In this case, both are potentially appropriate. The fact that the sentence itself is present time makes the past simple seem more appropriate to me than the past perfect, but that's a stylistic matter rather than a grammatical one, in my opinion. Using the past perfect could create a nuance of the damage having been caused a bit further back in the past, but I wouldn't rely on that as a solid meaning - just a sense.