Generally speaking, the expression "ganbare" is used to express encouragement and cheers to someone.
Simply put, it is the imperative sentence of a verb. Although emotion itself is not a command, it gives the impression of strong emotion.
If we only consider the meaning of the verb itself, we can take "hekome" as the antonym.
It is also an imperative sentence, and the verb itself means depression. That is to say, "give me a boring one!" This feeling.
But considering the daily use, it seems a bit strange.
If you consider semantics, you can also consider "Ganbaranakutemoii".
It means: it doesn't matter if you don't work hard. Generally, it may be used to comfort each other, or even to spit out that the other party is trying too hard.