The difference lies in the different scenarios in which the help is provided:
The icing on the cake is providing help on the basis of success and success, whereas the snow gives charcoal to the people in times of difficulty. Icing on the cake is easy, but delivering charcoal in the snow is rare.
1. Jinshang jianhua (锦上添花), a Chinese idiom with the pinyin jǐn shàng tiān huā , is a metaphor for adding good to good and beauty to beauty.
2. "Send charcoal in the snow" is a Chinese idiom with the pinyin xuě zhōng sòng tàn, which means to send charcoal to someone to keep them warm on a snowy day, or to give material or spiritual help to someone in times of great need.
Antonyms
1, 雪上加霜
Chinese idiom, pinyin is xuě shàng jiā shuāng, meaning a layer of frost on top of the snow, which can happen under certain weather conditions and is often used as a metaphor for a succession of disasters, with the damages becoming more and more serious.
Idiomatic usage: partial formal; as predicate, object, clause; with derogatory meaning.
2. Lujing Shishi
The Chinese idiom of luò jǐng xià shí (落井下石)
means to see a person falling into a trap, and instead of reaching out to save him, one pushes him down and throws a stone; it is used as a metaphor to say that a person is in danger when he is being framed.
Idiomatic usage: compound sentence; as predicate, determiner; derogatory.
Example: Why throw a stone at someone in a time of crisis is too unethical to be a human being.
Reference for the above: Baidu Wikipedia - Snow on Snow
Baidu Wikipedia - Falling down the well