sisyphist
/ˈsɪsɪfɪst/Definitions
1. noun
A person who is condemned to repeat a futile task endlessly.
“The worker became a sisyphist, pushing the heavy boulder up the hill only to have it roll back down again.”
2. noun
A person who is engaged in a task that is tedious and never-ending.
“After a few months, he realized he had become a sisyphist in his job, just going through the motions every day.”