Reward is related to Give. Give is the opposite of Pick. Pick is a type of Choose. 
Overwhelming is a synonym of Massive. Massive is a synonym of Enormous. Enormous is a synonym of Huge. Huge is related to Great. 
Reward <--RelatedTo--> Give <--Antonym--> Pick --IsA--> Choose 
Overwhelming <--Synonym--> Massive <--Synonym--> Enormous <--Synonym--> Huge <--RelatedTo--> Great 