dead loss
形容某人无用
Someone described as a dead loss is absolutely useless or a complete failure.
例句
When it comes to gardening, my brother is a dead loss.
说到园艺，我哥哥一窍不通。

class act
杰出的人
To say that someone, for example an athlete or entertainer, is a class act means that they are very good at what they do.
例句
Her career is just beginning, but she's already a class act.
她的事业刚刚起步，但她已经很杰出了。

happy-go-lucky
随遇而安，快乐的人
If you are a happy-go-lucky person, you are cheerful and carefree all the time.
例句
He's a happy-go-lucky sort of guy - always in good humour.
他是那种随遇而安，快乐的小伙子，总是很幽默。