I’m an international student. If I were not able to join/win an international competition(e.g. Chemistry Olympiad), what are the other extra-curriculars that show excellence and can be a big factor in your acceptance to an Ivy/top university?
Curing cancer is always a popular one.
For international studies majors bringing peace to the Middle East will boost your application.
Find something you are passionate about and do it well. Don’t focus on what other will think.
Or developing a universal vaccine.
You have a chance to separate from the pack by following your passions, being creative etc. It is highly unlikely your answer will come from people who never met you and have no idea about your particular talents, interests, etc.
Many years ago I went to MIT as an international student (I became a US citizen somewhat more recently, but still decades ago). In terms of ECs the approach that I used was just to do what I wanted to do. Because I was doing what I wanted to do, I did it well.
This is as far as I can tell the same approach that is recommended in the following blog on the MIT admissions web page:
If you get into leadership in any of your activities, then remember that “leadership” does not imply getting your way. Instead leadership means making the activity better for everyone. Usually this means listening. The sum total of good ideas coming out of everyone in a group is going to be better than the good ideas from any one person, including me and including you.