You have to dispute the debt amount and cheque as the details are not filled by you you can strech the case and you can ask him outside to compromise.
There can many defences based on reviewing complete documents as that regarding the cheque was obtained on trust for lesser amount and he cheated you and presented it with more amount also, dispute the debt that he doesnot owe you that amount so he has wrongly mentioned that amount and breached. Your trust.
Also though in case 138 if a cheques is given with signature than anyone can fill it balance of convenience remains in favour of that person now your job is to dispute same the cheque amount and debt.
See in case he sends you legal notice reply same with the facts that you both have agreed on payment of 16 lakh and now wrongly he is claiming 42 lakhs also the cheque was given on trust for only 16 laksh which he wrong filed in to 42 lakhs
Now the handwriting expert report in cheque can help you with the fact that other party has filed the details in cheque.
Also 138 case you will easily get a AB and it takes time.to proceed with case so you can ask the other party to compromise for a amount you can pay he will readily do.