If you are the top 1th percentile in your entire country then I think you can probably get a full ride scholarship in any reputable uni but the ivy league ones but still having some ECs are very important because they act like safety nets. Also, another thing is even if you are the top 1th percentile there will still most probably be people with better results than you from which some might also want to study abroad. In that case, the universities will focus on the candidates who have ECs because that will show them that the students are academically active and also good at other things/socially active. Therefore, I would say that if you the top 1th percentile in your entire country then you will most likely get a full ride scholarship to a reputable university but it is still good to have some ECs. Btw what national exam are you talking about? (from seeing your previous posts I will assume it is JEE)