Use ～きり to mark a hard limit — either a quantity/occasion that is the only one (一度きり、今回きり、二人きり), or an action after which nothing further happened (送ったきりで返事がない). In business writing it is handy for reporting a stalled process ("we sent it and that was that") or for drawing a line in negotiation ("this time only"). It is blunter and more final than だけ, so it carries a faint note of insufficiency or of no exceptions.