which haitian creole word is used to translate the verb toughen up?

It depends on what is being toughened up.
you can use the word andisi (to harden)
you can use vin rèd (to become stiff)
you can use mete gason sou or mete fanm sou (to be tough and strong)

Ou bezwen met gason sou ou.
or
Ou bezwen mete gason sou ou.
You need to toughen up. (if talking to a male)

Ou bezwen met fanm sou ou
or
Ou bezwen mete fanm sou ou.
You need to toughen up. (if talking to a female)
Haitian Creole ↔ English Reference, Look up Haitian Creole and English Words