Good stuff man. In addition to the extra detail needed during the initial flashbacks, the main thing that seems like it could use a little improvement is in the frequency content, especially since you're not competing with music here. You could have lower lows, higher highs and more dramatic transitions between the two. Running that moany ambience behind the whole thing risks washing it out and killing some of the dynamics you could have.
The shockwave at the end especially could use a little more design work, I'd want to hear the blast more than the dry sound of those rocks cracking -- though rocks at the tail end of it would be great too.
The character swings/whooshes are mixed really well, I was totally buying into the combat. If you wanted to you could add a little extra gack / jingles or some breaths and play them low just to get that stuff sparkling a little more, but totally up to you. Playing it clean and sparse with the SPFX moments you have (slo-mo) etc. works too.