what is the least rank that a general student should secure in JEE(mains) in order to get into an IIT?

this is very Good Query. IIT is One of the most Leading Examination in India for Engineering Courses.
Many Students want to take admission in IIT Colleges.
IIT Conducts Entrance Examination Every Year for Admission in IIT.

You want to know that what Rank Should Achieve for Getting Admission in NIT Colleges. IIT
Always Publish Cut-off Marks for Admission.
Cut-off marks is Different for Every Category.

If you Belong to Gen./OBC Category then your Cut-off Marks will High and if you belong to SC/ST then cut-OFF Marks is very low in comparison to Gen. Category.

you want to take admission in NIT Then you have to achieveRank 3000 - 5000.
There are many Colleges of NIT.
you have to achieve rank Between 3000 - 5000.
If you get your rank in between this then you will get admission in NIT College.
Thanks & Regards