what would you do to sb who did sth bad to you?

[Nathan Mckane]

Is this sentence correct?

I personally think it is. What about you?

what would you do to sb who did sth bad to you?

Thanks.

[Raymott]

Is this sentence correct?

I personally think it is. What about you?

what would you do to sb who did sth bad to you?

Thanks.

No. 'sb' and 'sth' are not English words, and it should begin with a capital letter. Otherwise, it would be acceptable.

[Nathan Mckane]

Thanks for the answer

Now would you please tell me which one is correct?

what would you do if you didn't study for a exam which was about to start in minutes?
what would you do if you hadn't study for a exam which was about to start in minutes?

[Raymott]

Thanks for the answer

Now would you please tell me which one is correct?

What would you do if you didn't study for an exam which was about to start in minutes?
What would you do if you hadn't studied for an exam which was about to start in minutes?

Neither is correct since, again, you haven't capitalised the first word. In English, this is mandatory.
I've corrected them. I would use the second version. You've phrased the second part of the sentence in the simple past tense form "an exam was about to start", so it's appropriate to use the past perfect for an event which happened (or not) before that event.
Of course, it's hypothetical; we aren't talking about two events in the past. But I'd still use the second version.