Dog is the opposite of Cat. Cat is related to Big. Big is related to Palace. Palace is related to Heaven. 
Crisis is related to Critical. Critical is a synonym of Crucial. Crucial is a synonym of Essential. Essential is related to Primary. 
Dog <--Antonym--> Cat <--RelatedTo--> Big <--RelatedTo--> Palace <--RelatedTo--> Heaven 
Crisis <--RelatedTo--> Critical <--Synonym--> Crucial <--Synonym--> Essential <--RelatedTo--> Primary 