Hi Robin,
What do you mean by dupe penalty? There is not one per se.
I mean if the dupe is claimed it's a violation and it can cause all kinds of problems, but not any direct penalty you can see.
But even if not claimed, a dupe can interfere with ranking which isn't really a penalty exactly, it's just nature of the beast.
Need more details about what type of dupe. (There are like 10.)
Why do you think penalty, what happened?
Claimed or not?
Same name? Or Different made up name or what was diff about the dupe?
Or Dr/atty dupes???
What do you mean by delete it???
Because if it's an additional listing claimed in dash, then that's violation and yes you need to delete from account. But that won't delete from maps if NAP is different.
So again need a lot more details about type of dupe and symptoms to be able to advise further.