Promising is a synonym of Encouraging. Encouraging is a synonym of Favorable. Favorable is the opposite of Bad. 
Envision is a type of Imagine. Envision is derived from Vision. Vision is related to Sense. Sense is related to Eye. 
Promising <--Synonym--> Encouraging <--Synonym--> Favorable <--Antonym--> Bad 
Imagine <--IsA-- Envision --DerivedFrom--> Vision <--RelatedTo--> Sense <--RelatedTo--> Eye 