Does a year gap post 4 years of work experience affect the chances to get into ISB Hyderabad drastically?

The Indian School of Business (ISB) Hyderabad evaluates each application based on merit, rather than adhering to a strict minimum or maximum criteria for years of work experience. Freshers may apply through the Young Leaders Program (YLP) or the early admission option. A break in one's career, as long as it can be justified, is acceptable. The quality of work experience, rather than the number of years, is what counts. 

Instead of worrying about any career gaps, focus on highlighting the relevant aspects of your profile. If the admissions team finds your application compelling, they may inquire about career gaps, but only after they have been initially impressed with your application.