Hi! Good improvements from the first draft! A couple of comments:
-I would shoot for a better opening - it doesn't really make me want to read the essay because I cannot help but picture you as a "typical" pre-med.
-I would not make reference to acing exams unless you are actually used to acing exams. You made reference to especially strong grades your senior year which suggests that you have not always aced exams...I could be wrong about this one, but it just doesn't make sense to reference being used to absolute excellence in academics if you have not always had it. Also, in general, you refer a lot to grades, and that may not be the best idea. This is about you and your spirit, bringing in grades so many times makes it seem like that was always your focus...
-you use some words that don't actually ring true. "Thrilling" is a good example. Even if it was a very exciting learning experience, I think adcoms are probably jaded. Most essays probably reference the "thrill" of scientific discovery (along with wanting to save the world) and it doesn't help to set you apart from anyone else.
-If you can, I would focus a little bit more on clinical experiences...you sort of mentioned that you did not have a lot of clinical experience, but I would not come right out and say that. If not clinical experience, talk about community service.
There are good things about the essay too, but you asked for critique so that is what I focused on. Good luck!