The correct answer is B: aggression.
Taking into account the context given in the excerpt by expressions such as "wrath", "Almighty God", "eternity", in addition to the novel's title, we can assume that the author is talking about some kind of punishment the character must receive. This is the reason is why we can conclude that "fierceness", in this context, dennotes aggression: an agressive punishment carried out by a wrathful God.
