When the chosen adjective is ‘powerful’, the one that immediately springs to my mind is Ennio Morricone’s score for ‘The Mission’. The climactic moment of the piece ‘The Falls’ coupled with the pictures of Angel Falls is very powerful.
Which leads me to think of John Barry’s score for ‘Out of Africa’. The original plan for that movie had been to use only standard classical repertoire, primarily Mozart. The decision to bring in John Barry was made quite late, and his score is credited as transforming the project from the more or less total flop it was heading to be into the moderate success it became. Again, the power of the music lies entirely in coupling the central theme with the pictures of Blixen’s lover flying her over the African landscape she had farmed for so many years but had never previously seen from that perspective.
I could mention several others – someone else mentioned ‘The Godfather’ and I have often wondered if it is well understood just how good Nino Rota’s scores for those films really were. But one more definitely worth a mention is John Williams’s score for Schindler’s List. There is a central difficulty with the subject matter of that film that any retreat into mere sentimentality would tend to trivialise something that retains deep sensitivities. I think that with his score, Williams walked the line very expertly between evoking an appropriate sense of the pathos of the situation without ever sliding into sentimentality. The result also warrants that same specified adjective.