For one's good:
为某人着想 √
例句:
She did that for your good.
她是为你着想才那样做的。
Good egg:
好的鸡蛋 ×
好人 √
He is a good egg, I'm sure you will like him once you get to know him.
他是个好人,如果你跟他混熟了,肯定会喜欢他。(内容来自学英语口语,如有侵权请联系删除)