Е-18

КТО НИ (НА) ЕСТЬ coll NP subj or obj fixed WO

it is inconsequential who, any person or people who might be involved, regardless of who he or they might be

anyone (anybody) at all

absolutely anyone (anybody) anyone, it doesn't matter who anyone who is available (who can etc) (only when все or каждый is stated or implied) anyone and everyone everyone and his brother (uncle etc).

Заприте шкаф с документацией: нельзя, чтобы кто ни на есть приходил и брал то, что ему нужно. Lock the file cabinet: we can't have anyone and everyone coming and taking whatever they need.