How do I delete accidental duplicate artist tags?

Accidentally made koyake3 because the script I use didn't recognize the artist's twitter profile, how do I delete it?.

You can't delete the entry in the sense of making it so that there is no entry to begin with, but by going to the entry, clicking the Edit button on the top and then clicking Delete at the top, you'll 'delete' the entry (read: make it so that the system doesn't reference it for future use). If you want to cleanly 'delete' an entry, transfer anything that the active artist entry doesn't have to said entry, and remove it from the duplicate, only leaving the name of the active entry in the "Other names" section of the duplicate entry.