An executioner executes a sentence
An undertaker undertakes a task

Are there other occupations where a (general) verb has become the noun?

Lots of too-specific examples in reply, but 'undertake' and 'execute' are general verbs, and could be done for many jobs

Every reply so far is too-specific

This is a good one https://twitter.com/FiniteMonkey/status/1317872422503198720

Thank you for all the specific examples (build/builder etc), but few of the verbs are as general as 'execute' and 'undertake'

Almost all occupations involve executing or undertaking tasks, but only two distinct (and rather unpleasant) jobs ended with the related job titles

I am writing something about executioners, and it just struck me that the word itself is odd

You don't think of them 'executing the sentence of the court' when you use the word, but killing someone

Another good example of the most general of terms acquiring a somewhat unpleasant meaning https://twitter.com/jackschickler/status/1317875816538189824