Game 1:
:07 - You should have grabbed/tilted instead of Nair.
:10 - You mis-spaced your Uair and you were punished for it with Bair.
MISC. :13 - You could have fast-falled and auto-canceled.
:15 - After the first Uair, you should have buffered a FFUair (reset the juggle minus one of your jumps)>Dair(punishes the air dodge to pass through Uair) to allow you to react and punish virtually all of his options. Because you buffered it incorrectly, you Daired into the ground and were grabbed for it. Dairing into the ground isn't safe.
:22 - You had a very good potential edge guard position from his DI, but you whiffed a Fair away from him. Also, be careful with your buffering; you whiffed a Dtilt after hitting him and gave him a guaranteed Ftilt that he didn't take.
:29 - You wouldn't have been punished if you went to the ledge instead.
:32 - In that position, he could have blown C4 and been safe (even if you power shielded it) or he could have blown C4 and hit you (even if you normally shielded it, C4 does a lot of damage to shields; he could have poked you with a large amount of his move set for a fair amount of time afterward). Neither option is good for you.
:33 - He had a free grab when you glided into him at that spacing.
:36 - You could have space a Uair and stayed closer into the stage so that he would have as much of a reward even if he hit you.
:46 - You mis-spaced Uair and improperly buffered Dair again.
:51 - You had a guaranteed/free weak-Nair or B, and more things that would have frame-trapped him (Nair/B/etc. would have knocked him off of the platform and hit him before he could do anything except B with strict timing on his part).
:55 - He had a free grab/Ftilt/C4 sticky if he had just air dodged on the way down reaction. Also, Up-B shouldn't have worked. Even with DI up, he could have still survived that on a very surprised and naturally slow reaction. I'm not sure why Sync didn't.
1:01 - That was a poor decision on both accounts.
1:06 - You could have gone to safety, but instead you grossly over-committed yourself and into a grenade (it could have been worse if he just went for a harder punish, which he probably should have).
1:09 - Don't randomly Uair or Dair while you're following. It leaves you uncovered and in lag, respectively. If Snake is using proper timing, Bair/Uair becomes good options.
1:21 - That mis-spaced Up-B costs you a potential gimp.
MISC. 1:29 - Up-B would have taken his stock when he dropped that C4, although that isn't always the best option.
1:39 - Don't Uair>jump>Nair. There's several options here, but I believe that the proper one that you were going for would have been a buffered Uair>FFNair.
1:40 - Practice DIng properly during grabs/tilts/etc. until it becomes habit. You should not have died.
1:47 - Try using a rising Dair instead.
1:52 - Why would you Dsmash then?
1:59 - You should have either followed him in the air or at least reversed the Up-B so that you could follow him later, rather than the total safety he had after you used Up-B. Also, you should have drifted to the ledge so that you wouldn't have been open to that C4.
2:05 - A ledge-released Dair would have ended his stock.
2:24 - You mis-spaced against his grenade and took free damage.
2:26 - Failed DI chase/poor buffering aside, Nair would have probably been a better choice of Uair if you sweet-spotted it, as it would have been guaranteed damage and could have led to Uair anyway (FFNair>Uair>stuff).
2:31 - Although it can work as a mix-up, Brolling out of Snake's Dthrow is his worst option. Get-up>grab, get-up attack, and Froll are [much] better. Just remember to keep things fresh and think of what your opponent will do.
2:40 - You mis-spaced an important Uair that also could have been Up-B, Nair, Fsmash, etc.
MISC. 2:50 - That wasn't worth it.
2:59 - You used another rising/mis-spaced Uair.
3:04 - That was a semi-guaranteed DACUS (the dash attack would have hit you, but I don't know if Usmash would have covered your possible landing on the platform.
MISC. 3:06 - Arguably not worth it.
3:10 - That wasn't safe, it should have been your stock, and it was an uncommon read (it wasn't necessarily a bad read in that it could happen, but not many Snakes Up-B directly in front of Meta Knight.
3:15 - Uair>Uair>Uair doesn't generally work well. B or Uair>jump>FF>Nair would have worked nicely, but he could have Utilted you on the latter. Either of those options would either hit him or knocked him off of the edge (and into B if you were using B).
MISC. 3:48 - Jump>Up-B would have ended his stock, but -- again -- it would have been a read and not necessarily safe.
3:50 - A spot dodge on reaction or a roll (preferably backward) would have allowed you to avoid the C4 explosion and to continue with your momentum instead of losing it and allowing Snake to set up a defensive position while you climbed back onto the stage.
3:52 - Again, dash grabbing at Snake isn't safe. That was a Utilt.
4:04 - Another rising/mis-spaced Uair and it cost you your stock.
MISC. 4:11 - It wasn't necessarily bad (it was a kill move and -- had he not power shielded it -- it probably would have pushed him off of the ledge, so it was safe), but he could have punished that Dsmash or just run up and shielded your next Dsmash.