I want to know how to say, "What's your problem?" as an insult in Mandarin.
你很多問題勒神經病嗎““5”4””4 再來你有病嗎 是沒去看醫生嗎
If you wish to express
What's your problem?
this in the sense of
Do you have a problem with that?
you can say
意见 means, in general, opinion, comment or suggestion. (Compare with 建议 which possesses a similar meaning yet with a softer connotation). The former may suggest there is a variance in opinions to the extent of contention, while the latter describes a suggestion in the sense of a non-dictating recommendation.
Depending on your tone of voice and context, 意见 may convey a different attitude, but it tends to sound argumentative in most cases. Consult this.
Do note that this way of expression might get you in trouble, so use your words wisely! :)
Or even simpler
In a similar vein, if you want to call someone crazy
Its original meaning is
There is another popular saying