grant (someone) no quarter

To offer (someone) no mercy, concession, indulgence, or leeway. This match determines if we're heading to the finals of the tournament, so go out there and grant them no quarter! Our boss grants no quarter when it comes to the standards of our projects.

granted no quarter

To be offered no mercy, concession, or indulgence. We are at war with barbarians, soldier. You will be granted no quarter if you are taken captive; likewise, you shall grant them no quarter should you take them alive. This match determines if we're heading to the finals of the tournament, so make sure they are granted no quarter!

grant someone no quarter

and give someone no quarter

Fig. not to allow someone any mercy or indulgence. (Originally meant to refuse to imprison and simply to kill one's prisoner.) The professor was harsh on lazy students. During class, he granted them no quarter.