adj. 25B6; adjective
he is unsparing in his criticism : MERCILESS, pitiless, ruthless, relentless, remorseless, unmerciful, unforgiving, implacable, uncompromising; stern, strict, severe, harsh, tough, rigorous.
unsparing approval : UNGRUDGING, unstinting, willingly given, free, free-handed, ready; lavish, liberal, generous, magnanimous, open-handed.