Dirty is the opposite of Bright. Bright is a synonym of Encouraging. Incentive is a type of Encouraging. Incentive is a synonym of Bonus. 
Feeling is related to Care. Care is related to Assistance. Assistance is related to Help. Help is related to Aide. 
Dirty <--Antonym--> Bright <--Synonym--> Encouraging <--IsA-- Incentive <--Synonym--> Bonus 
Feeling <--RelatedTo--> Care <--RelatedTo--> Assistance <--RelatedTo--> Help <--RelatedTo--> Aide 