How to deal with co-authors' tardiness?
The correct answer is not to wait until two days before the deadline to check in on your co-author's progress. Presumably this is no longer an option.

If the section is not necessary, take it out. If it is necessary, you and your non-tardy co-authors can try to get together and do it together before the final deadline. 

You should certainly tell the tardy co-author what you plan to do (I mean the collective "you," as in you and your other co-authors). 

If the tardy co-author's contribution doesn't make it in before the final deadline, then his name won't go on it either.

Note that if this was a paper being submitted for publication, e.g. a conference submission, and not for school, you would likely just miss this deadline entirely and have to wait to submit to another conference.