Complex sentence: The colonial reports about infanticide, particularly of females, were primarily from Christian missionaries proselytising in India who sent letters back to Britain characterising the culture as "savage, ignorant, depraved" followed by statements of their missionary accomplishments.
Split into simpler sentences: The colonial reports about infanticide, particularly of females, were primarily from Christian missionaries who were proselytising in India. They sent letters back to Britain characterising the culture as "savage, ignorant, depraved" and announcing their missionary accomplishments.