Prevent is a synonym of Keep. Keep is the opposite of Give. Tender is a type of Give. 
Massive is the opposite of Tiny. Tiny is related to Grain. Grain is related to Hour. Hour is related to Segment. 
Prevent <--Synonym--> Keep <--Antonym--> Give <--IsA-- Tender 
Massive <--Antonym--> Tiny <--RelatedTo--> Grain <--RelatedTo--> Hour <--RelatedTo--> Segment 