Nemo Cassandrae res futuras praedicenti credebat.
How about this explanation ?
Nemo : the subject of the sentence
Cassandrae : dative case, which credere takes as its object
res futuras : accusative case, which praedicere takes as its object
praedicenti : dative case of the participle which modifies Cassandrae (Cassandra foretelling, Cassandra who is foretelling)
credebat : the main verb and predicate of the sentence, the subject is nemo, the object is the dative case of Cassandra