Regret is a synonym of Grief. Grief is a synonym of Failure. Failure is the opposite of Success. 
Butterfly is etymologically related to Fly. Flight is a type of Fly. 
Regret <--Synonym--> Grief <--Synonym--> Failure <--Antonym--> Success 
Butterfly --EtymologicallyRelatedTo--> Fly <--IsA-- Flight 