Definition of a nasty one in English:

a nasty one

phrase

informal
  • An awkward question or task.

    • ‘‘That was a nasty one,’ Eric commented jovially, melting out of the trees in his brown uniform.’
    • ‘I knew his expressions too well, and he would defiantly give me a nasty one this time.’
    • ‘This particular module was a nasty one: it modified the behavior of certain system calls to hide itself from the lsmod command and to hide the presence of scanners, crackers, sniffer logs and other such files.’