Concept:
Prefixes play a vital role in determining the "attitude" of a word towards people.
• Prefix 'Mis-': In this context, it comes from the Greek 'miso', meaning "to hate."
• Prefix 'Phil-': Means "to love" or "affinity for."
Step 1: Analyzing the Roots of the options.
Phil (Love) +
Anthropos (Mankind) = Lover of mankind.
Mis (Hate) +
Gyné (Woman) = Hater of women.
Cynic = A person who believes people are motivated purely by self-interest.
Step 2: Identifying the Hater of Mankind.
Mis (Hate) +
Anthropos (Mankind) =
Misanthrope.
A misanthrope avoids human society and has a general distrust of human nature.
Therefore, based on the etymological breakdown, the correct one-word substitution for someone who hates mankind is a Misanthrope.