back-breaking

trabalho de quebrar as costas

Refers to any form of extremely demanding physical job or task.

Similar to 'work', but often implies manual, unskilled, and prolonged effort.

trabalho extenuante

More literary or formal than 'work' or 'labour', emphasizing the wearisome and unpleasant nature of the hard work.

Refere-se a um trabalho extremamente árduo e fisicamente exigente.