Will the placement drive accept the students with grace in one subject?

That's right, #-Link-Snipped-# .

#-Link-Snipped-# - most of the companies will ask for 60% throughout performance. If you have that - you're all set. There will be only a few companies that will actually care for all the mark sheets. 

The reason companies are getting stricter with their selection criteria is because the number of engineering graduates wanting to appear for the campus placements is growing every year. Companies need a way to screen only the top candidates so that the overall burden of evaluating them is minimized.

I've been a part of several placement drives and I can tell you for sure that evaluating candidates is a huge task. By setting up the placement eligibility criteria; that problem gets addressed to some extent.

Now that you've already had a back and then cleared it in your second attempt, all you need to do is focus on other aspects of the campus recruitment. It could be cracking the aptitude tests, technical and HR rounds of Interview. 

I'll also recommend talking to your college's placements coordinator to check if the visiting companies have mandated 'no back' policy for students appearing. Their answer will be more authoritative in this case.