嘴不饶人心里善心不饶人嘴上甜
[zuĭ bù ráo rén xīn lĭ shàn xīn bù ráo rén zuĭ shàng tián]
'Unforgiving With Words But Sweet On The Inside' characterizes individuals whose exterior may seem harsh or critical (with sharp tongues) but are actually kind-hearted underneath, showing that outward demeanor isn't always reflective of true personality.