When insulting someone in this way, you should be speaking in a nice tone.
在侮辱人的时候，通常会用一种听起来似乎很友好的语调。
A good way to do this would be to use a compliment first then an insult at the end of the sentence.
一个很好的方式是，先淡淡地表扬一句，再骂他！

Things you can insult someone on in English:
在英文当中，侮辱人通常从这么几个方面下手：
looks or general appearance 外貌
I like those pants. Does your grandma know you're wearing them?
哇我喜欢你的裤子诶，你奶奶知道你把它穿出来了吗？
You look like a train wreck.
你看起来就像火车残骸一样破破烂烂的。

smell or hygiene 气味，体味
I can smell you from a mile away! When was the last time you had a shower?
我从一英里外的地方就能闻到你了！你上次洗澡是什么时候？
I can actually see the stink around you.
你都臭到发绿光了你知道吗？

intelligence 智力，智商
You aren't the sharpest tool in the shed. / You aren't the brightest bulb in the box.
你不是这棚里最锋利的工具。/ 你不是这盒子里最亮的灯泡。（你脑子不灵光。）
I envy all the people who haven't met you yet.
我真是羡慕那些没有遇见你的人。
If you weren't so cute, life would be much harder.
你要不是这么可爱的话，生活一定会很艰难吧。
Did your mother drop you on your head when you were little?
你小的时候你妈妈是不是摔过你的脑袋？
Did you eat paint chips when you were a child?
你小时候是不是吃过油漆块？
Did you grow up under telephone wires / under a power cable?
你是不是在电话线 / 电缆下面长大的？