Can you leave Qatar with bank loan?

dont think so.

I will assume by leaving you mean not intending to come back; although it is not ethical, yet you can do that.
Also you will have to consider that all GCC countries are linked through a police system; i.e. if you left Qatar and headed to Dubai, you could get arrested there and resent to Qatar for prison.
From what I heard, few Arab countries (I know it is one country so far) have signed an agreement with Qatar, by which you could also be pursued in the such country (other than GCC)

yes you can.

Whether your are asking question to me, if not correct your question.
Secondly if you want to leave qatar with your loan in bank.You must ask your bank authority to clarify the matter and inform to your sponsor about this. Then follow the rules of agreement what you have done while taking the loan. you will get the answer.
If you are honest and sincere you never ask this question.

If the loan is granted based on Salary Transfer, the company that you are working for are commited to inform the bank at your end of service, the bank will call you to ask for the settlement, and there if it did not happen, then they will apply a travel ban, so you cannot leave the country.

if the bank is not informed,try to send them the installments every month by TT to your account, if in case you failed to pay the installments, then they will deposit your security cheque and file case against you in the court,so upon your return you will be arrested at the gates, if only they know where you are!! they will send the case to a collection company in that country to open a legal case, and there you should hire a loyer,the Interpol is for Crimes or large amount of money and from case to case, my advise to you is to keep up a good relationship with the bank to avoid any hassels in the future.