Usage patterns
〈事〉が徒労に帰すfor something to come to nothing / prove fruitless
Years of research came to nothing.
〈事〉は徒労だったsomething turned out to be a wasted effort
I tried to persuade him, but it turned out to be futile.
〈動詞〉のは徒労だit is futile to (do something)
Opposing it now is a pointless effort.