See, if I don't sugar-coat my words then your class XIIth marks might be a hurdle for you in the final placements in JBIMS. Since good companies like in consultancy domain or Investment Banking always check if you have a good background in academics right from your class Xth.

However, you can reduce your effect of your class XIIth with your increased scores in graduation and winning some major competition. Try to make a weel rounded profile and you'll flourish. All the best!