Hi Sourav,

Sorry to say you that your question is a bit stupid. This does not make any sense. No institute can guarantee you 100% success rate as IITs have students from different states, different sections of society, etc. This in itself is proof that no institute can give 100% rather different institutes combines their results along with students who do not join any coaching. Rather than focusing on institutes reputation, you should be focusing on your academics. For a seat in IITs is a long road. You need a dedicated preparation for two years and then it is a cake walk. However, there are few institutes which help you achieve your goal for a seat in IIT.

• ALLEN INSTITUTE, KOTA
  
• FIT-JEE, DELHI
• RESONANCE, KOTA
• VIDHYA MANDIR, SOUTH INDIA
• AAKASH, DELHI

These are not the only institutes available but these are some of the best in the market.
Here are a few important links:-

https://engineering.careers360.com/articles/how-prepare-for-jee-main
https://engineering.careers360.com/exams/jee-main
https://engineering.careers360.com/articles/top-5-tips-to-crack-jee-main

Hope this solves your query.
Comment your doubts, if any.

All the best. Thank You.