bum 饭桶
scallywag
sculpin

1. 格林先生总是盛气凌人的样子。其实，他是个饭桶。
Mr Green is always on his high horse. In fact, he is good for nothing.

2. 你真没用！你是个饭桶！
You are good for nothing.

3. 不懂装懂,永世饭桶.
He who knows nothing but pretends to know everything,is indeed a good-for-nothing.

4. 不懂装懂永远是饭桶.
He who knows nothing but pretends to know everything,is indeed a good-for-nothing.

5. “他干那工作在行，是不是。”“你是在说笑话吧，他是个十足的饭桶。”
“He’s very good at his jobs, isn’t he?”“You must be joking! He’s absolutely useless.

6. 呵呵，直到有天有个叫洛哈特的饭桶当了黑魔法防御术老师，情况就不同啦。
Well, not until a certain git by the name of Lockhart took over as Defence Against the Dark Arts teacher, at any rate.

7. 你这个饭桶！我命令你，不惜任何代价，都要拿到它！否则我就会把你流放到美国去过苦日子！
You foolish! I order you no matter what you do, you must get it, otherwise you will be sent to USA to suffer!