sarcasm
Imagine how these things might be said with the opposite meaning:
"Oh, that's great. Just great."
"You were a big help."
"You didn't have to be so generous."
Those could all be sarcastic remarks.
noun
Irony states the opposite of the writer's intent to get the point across.
Doubling and subtracting 1
When something happens that is the exact opposite of what you expected to happen, this is called irony. An example would be getting candles to relieve your stress and them accidentally burning the house down.
'kanojou' would be the exact, but when stating something like 'girlfriend-boyfriend', it would be simply 'kano-kare'. I hope I helped = )
The opposite of "ask" is "answer".
The exact opposite of logical is illogical.
Bear in mind that not all words have an exact opposite. You might say that the opposite of making an enquiry is to remain silent and make no enquiry. Or you might say that the opposite of making an enquiry is replying to an enquiry. Neither of these is exactly an opposite but they are at least something like an opposite.
The opposite of hymn is Christian Metal. The exact exact opposite is secular metal (aka songs that have a bunch of swear words, etc.)
As a metaphor is a a figure of speech which is applied to something to which it is not strictly applicable, the opposite would be the concept of 'le mot juste' - the right word, the exact word, or maybe 'apposite'
Antidiarrheals are the exact opposite of laxatives.
Strength. Forte. (There is no exact opposite.)
A reaction that is the exact opposite of what was therapeutically intended is a paradoxical reaction.