The point  u/s 138 of NI Act "Tthe cheque so issued must have been issued in discharge, either in whole or in part, of a legally enforceable debt or liability;" need a small clarification. Suppose, Mr. A - a Broking House Executive - posing himself as an expart in Stock Market , takes Rs. 5,00,000.00 worth of Stock of Mr. B under his controle without ant written agreement. Mr. A forces of Mr. B to buy/sale as per Mr. A's instructions only to generate huge brokerage for his company and by this process looses whole stock portfolio of Mr. B. After being cought, Mr. A gives a written undertaking on a plain paper assuming his responsibility to pay Rs. 5,00,000.00 to Mr. B. Afterward Mr. A gives a cheque of Rs. 5,00,000.00 from his personal account to Mr. B which - when deposited by Mr. B - was dishonoured by the bank for 'Insufficient Fund'.

Now in this case, can Mr. B move to the court u/s 138 satisfying the point above? Is this a legally enforceable liability on Mr. A? Can a cheating case u/s 415 be done on Mr. A if he denies his liability? What other ways to take to brought Mr. A to book and get back the money?

1. It is a legally enforceable contractualy liability.

2. 417 is also attracted. 

This is an all India problem. Find out there may be other persons also similarly cheated. File complaint with economic offenses  wing of police.

However not much hope to get back money., the person can be convicted and sent to jail.

1. Mr A Forces Mr B to buy/sale. In general this means that A gave bad advise but all the transactions were carried out by B in his (B's) account only.

2. When caught, A must have felt guilty or cornered and gave the assurance in writing that he would pay and he issued a cheque which got bounced.

If this is the truth and both complainant and accused approach the court with this truth and dishonored cheque, then I am afraid the court in all likelyhood is going to acquit the accused. This is no legally enforceable debt. This is no cheating either, at the best this is the professional misconduct that due to his not so competent advise B lost heavily.

While lost all the stocks, Mr. A still tried to conceal the fact from Mr. B. Moreover, he engineered to give a 'False Voice Confirmation' by his men to give an impression that. Mr. B still have some investment left. Mr. A asked for Rs. 1,00,000.00 from Mr. B to introduce again into market so that the loss can be recovered by the left over investment & Rs. 1,00,000.00. Whereas, in fact, there were nothing left. All these False Confirmation and Mr. A asking for fresh introduction of money - has a voice recording with Mr. B. Moreover, there are several voice recording with Mr. B which can prove Mr. A always accepted his responsibility for the loss. 

In the light of the voice data and the bounced cheque, can Mr. B get his money back?

It is not clear how A was operating on behalf of of B.

For the period of his 'management', Mr. A forced Mr. B to trade only in derivatives - knowing fully that Mr. B has no understanding about the derivative trading atall. Mr. A used to call from his personal mobile to Mr. B, asked him to note down the orders and just echo them to place his order .Thereafter asked the person at broaking house to phone Mr. B to take his order. Besides, Mr. A himself did few transaction even without letting Mr. B to know - which he later admitted over phone. Mr. B has a voice recording of all these through his mobile phone. And Mr. A has siphoned out 70% of the portfolio value of Mr. A as brokerage. By doing this, Mr. A has proved his worth to his company and got incentives and a may be a lift in his designation.

It is seen that, cheats who took money /  jewellery from innocent people to double / triple them, also got punished when cought. If that is the case why Mr B will not get justice for his mistake of believing a higher executive from a reputed broking firm?

Moreover, as per SEBI guideline, no one from a broker's end can influence / force a client. After very first transaction, Mr. A even threaten Mr. B - if Mr. B stops derivative trading now, all his portfolio will be lost as " buy position", "sale position", "hedge position" etc. etc. are entangled in such a way that it can not be stopped misway and Mr. B had to follow Mr. A's instructions every day for 14 days till all the stocks were squered off to meet the loss of derivative trading.

Mr. A must be brought to book for (1) cheating Mr. B by posing himself as Stock Market Guru; (2) breach of trust of Mr. B by destroying his full portfolio; (3) forgery for engineering false 'Voice Confirmation' to extract another Rs. 1 lakh from Mr. B.

If a person like mr. A is aquitted, he may harm maney more person for who bearing Rs. 5 lakh would be end of their life.

Is there any ray of hope?

It is true that A has played with B. But no trading house will give blanket assurance for any gains, since all the transactions were ultimately carried out on behalf and on instruction of B, so B cannot say that he was ignorant and he blindly went ahead on A's advise, 

having said that you can take followinga action:

1. File the case u/ S.138 of NI Act. Hire a good lawyer first and then proceed. This will put pressure on him and send a copy of this to brokerage house. You should know that A may be acquitted in this case, so please preaper hard and file. 

2. File an FIR for unauthorised use of B's funds (somewhere you stated that A traded without confirmation from B). This will take care of A.

3. If you have evidence of any force, file a complaint against the brokerage house also with SEBI.

If Mr. A himself accepts his liability at court, can it be "legally enforceable liability" ?

In criminal cases admission of accused certainly goes against him, but courts look at all the aspect before convicting, self confession prima facie may not result into conviction, it has to be supported by evidence on record.

My observation is solely based on information provided in this forum by you, and on the face of it the court may not convict u/s 138, for one very simple reason also that all the transactions were carried out in B's account only, A's role was to give only bad advise, probably to enhance his brokerage. Other cases as suggested above in Sr#2 and Sr#3 can also be pursued and they have better force.