Apart from CAT,, the weightage is given also for 10th and +2 marks, so how much % is the requirement in MDI?

Initial shortlist is done on the basis of CAT score. 50% marks is required for 10th, 12th &

graduation.

What the admission cell actually looks for in the past academic records is consistency in your performance and as you have decently scored in 10th and graduation, they would understand that due to certain reasons you could not score well in 12th. Let me tell you one thing that the admission cell of all the colleges is very understanding, in terms that they don't stop options of a deserving candidate just because of low marks in one term or class. But yes, your 12th marks must not be below the set eligibility criteria i.e., 50% for general and NC-OBC category and 45% for SC/ST/PWD. Also there have been cases in the past, where students with 60% in some or the other classes, have been admitted to top B- schools, provided they gave honest and justifiable reasons when asked. For MDI, try to score above 90 percentile in CAT.
All the best for your future!!