Alright, I'll tell you what I could see, take from it what you will. If someone notices something wrong or incorrect about this analysis, please let me know. I don't want to impart any wrong information.
0:00 - Good start. Utilt OoS, CG > fthrow, good stuff. However...
0:10 - You dash away from the edge giving up ledge space to Peach. This isn't so bad because you retaliated to her actions at the ledge with a bair that sent her back offstage, but then...
0:15 - Peach fairs underneath the ledge, dropping even further underneath it. I would have taken this chance to quickly grab the ledge. In fact, I would have gone for it the moment I saw Peach falling with a fair underneath the ledge. She still had her float, I believe, so it wasn't a guaranteed kill, but if she was as upB trigger happy as I just saw, you probably would have ledgehogged her earning yourself an extremely early first stock lead. As it went down however, you kind of gave Peach the ledge, even though she put herself into a really bad position and seemed to have all the wrong reflexive reactions for that very situation.
0:18 - OK, interesting call. No one can argue with what you did because you tried to read Peach's action off the ledge and those things are hardly debatable. Reads are intrinsic like that. However, your spacing was all wrong. You were way too close to the ledge to reasonably Inhale anything. A couple steps back would have been fine.
0:21 - Uh oh, you're starting to look like a spot-dodge happy DDD. I used to be like this and it wasn't until someone else criticized me on the habit that I broke out of it. DDD's spot-dodge is broken, but that doesn't mean you should use it all the time. In this particular case, you spot dodged
after Peach hit your shield with an fsmash, giving up a perfectly good opportunity to grab her. Peach is one of the more difficult chars to grab reliably. You want to take advantage of every chance you've got.
0:22 - Yeah, you're really spot-dodge/air dodge (AD) happy. Right after the spot dodge, you jump away and AD when a bair would have covered you just fine. Peach can't really challenge our bair (not many chars can) and definitely not when we're retreating with it. I'm telling you right now that if you had baired, you probably would have hit her cleanly because she was chasing after you with a dair while right next to you. Instead, you had to go for a trade, which isn't
bad, per se, but you could have received much better rewards.
0:24 - I'm not sure what the Peach did, but it made her land with some lag that you could have punished with a grab. Learn to realize your grab opportunities and nab 'em! Now, you shielded in anticipation of something, which is fine, but your following actions weren't so fine. Peach spot-dodged in front of you and you ran away instead of punishing it. You must realize that everyone is aware of DDD's CG capability and no one wants to be grabbed for big damage. This is one of these subtle things you have to understand and
use to your advantage as a DDD main. Read the spot dodge and react. When she landed in front of you with lag, you missed the opportunity to grab. That's fine. Read the subsequent spot-dodge and punish THAT. You can even use your 'fear factor control' to afford yourself chances to utilt the opponent for the kill instead of grabbing them. Unfortunately in this situation, you ran away, jumped, and DJ'd towards her, another puzzling action because it took away your ability to bair and protect yourself, which allowed her to pressure you afterwards.
0:30 - Stop that.....shield...stuff. Bair away and reset the situation. Even if you PS'd the turnip, you wouldn't get much advantage. I usually either want to be facing Peach so that if I have to shield, I might be able to land a shieldgrab off of it, or if I have to face away, be bairing so that I can reset the situation and possibly nab some damage while at it.
0:32 - Good jab > grab! I personally would have gone for the grab attempt after jab 1, but what you did worked too. Good stuff! However, you didn't maximize the punish. You went for bthrow instead of a dthrow > bthrow. As I said, grabbing Peach can be hard so we want to maximize our punishes here.
0:35 - Good grab, good dthrow. Just wanted to note that dthrow > ftilt is a true combo on every single character that we CG. It seemed like you were looking for something to follow the dthrow up with, so try that sometime. Tbh though, it seemed like you had enough room for just one more re-grab, but if you don't wanna risk it, ftilt away!
0:38 - You definitely had enough room to CG here! You could have dthrown once before that fthrow. Maximize your punishes.
0:41 - Again, you let Peach drop with a fair way below the ledge, using up her float in the process, and you didn't grab the ledge so she got it. She seems pretty upB trigger happy when she's put in that situation so jump on that ledge the moment you see her fall with fair like that,
especially when you see that she used her float beforehand. Without her float, she can't try to stall out your invincibility and she was
really low.
0:43 - I don't know how familiar you are with fighting Peaches, but her float cancelled (FC) aerials have only 2 frames of landing lag, which is exactly the same as just landing on the ground with nothing, so don't try to punish that. That FC fair actually had
positive frame advantage on your block. I know, it's messed up, but that's how Peach is.
0:45 - Oh noooooo! She fsmashed your shield
again and you didn't grab her but jumped instead!

OK, that's ok, just capitalize on the next time. However, when you land in front of her shield, you utilt her shield instead of grabbing it. You need to learn about DDD's landing grab mix-ups. DDD's aerials, especially his bair, are threatening enough that they often scare his opponent into shielding when he's in the air close to him. You can use this to your advantage by landing quickly and grabbing him. DDD is imposing like this. After all, he
is the KING!

Manipulate your opponent's fear of being kicked and grabbed. This is our form of pressure.
0:47 - Ok, stop that!

You could have shielded any of those
three fsmashes and landed yourself a free shieldgrab for Peach's carelessness. Even if one of them had hit you, it would have done almost nothing at your current %. You are heavy and Peach is fairly weak (fairly).
0:55 - Ooooh, good read!
1:10 - Well, you got a CG, which is great, but you didn't follow up with something suitable. I
think you had enough space for one more re-grab, but even if not, don't forget about dthrow > ftilt.
1:19 - I would suggest not to pummel your opponent if he is below 50%. It is way too easy to mash out before the throw at those %'s and it's not worth it. Stick with the CG.
1:24 - Stick with the CG.
1:32 - Tough situation you were in, airborne at 152% and running out of jumps, but I would have turned around during one of those jumps to allow myself to at least attempt to protect myself with a bair. Alternatively, if you have to land and you want/have to face front, you can protect your landing with Inhale. It's pretty nifty like that.
1:43 - Really good pivot grab right there.
1:50 - Dude, I'm not gonna say that your foxtrotting back and forth is bad or anything, but I really think it's causing you to miss some prime opportunities. You seem more focused on foxtrotting then actually winning your match.......which is fine if that's what you want.
1:54 - Darn tripping!
1:59 - If you're gonna land right on top of your opponent, I think you should land with Inhale. I know I said regular landing lag is only 2 frames, but that still makes it punishable if the opponent knows you're going/have to land.
2:03 - The CG, man... Honor does not control King DDD. King DDD controls honor!
2:08 - Think of all the damage you could have inflicted through CG's by now.
2:12 - Good plat drop fake-out! :D
2:14 - That was a weird and awkward position for you to try to utilt Peach from. The situation called for grab.
2:16 - Why were you jumping right in front of Peach like that right before she grabbed you? The situation called for grab, utilt, or dtilt, maybe an Inhale, but not a jump.
2:20 - You ledgejump AD'd to try to get back onstage while avoiding that turnip 'wall'. I have no gripes with that. However, I think you went to too much trouble to scurry through Peach's ledge pressure when you could have just eliminated that pressure altogether. Peach was still picking turnips when you grabbed the ledge. I would have ledgehop faired her to clear her away from that space. It probably would have hit her for some big meaty damage, and even if it didn't (she shielded or spot-dodged it), it would have given her the message, "HEY! I've got a really big hammer here and you're standing right within range of it, so CLEAR OFF!!!" No one wants to stay close to the ledge when they see that DDD's not afraid to swing that hammer around.
2:27 - See? I find it's usually best to attempt to grab after jab 1 if you're going for a jab > grab at all. In this case, she did indeed shield the second hit, just like the last time you tried this. However, remembering what happened last time this same exact situation occurred, Peach spot-dodged the grab and ftilted you. Now, if you had grabbed after the jab 1 instead, it definitely would have gotten her because she shielded the jab 2. Remember that you can grab after either jab 1 or 2, so mix it up.
2:50 - From this point on, you seem to start playing really impatiently because Peach has gotten the lead. Relax and play like you normally would, especially since it was winning you the match up until that point. Don't worry about catching that lead right away because you still have plenty of time (5 minutes and 10 seconds to be exact). It wasn't even that big of a lead because Peach was at kill %'s anyway. One utilt and that stock is over. Just be patient and wait for your chance. Don't force things. Funnily enough, the change in music matched this change in mood perfectly!
3:04 - Peach floated over you with a fair. Kick her in the butt for that! Don't wait to grab her when she lands because remember, FC aerials have practically no landing lag.
3:15 - Ok, NOW you're getting aggressive with your edgeguarding, but it seems to be an act of desperation rather than what you normally do. If you're going to edgeguard, do it throughout the entire match, not just when you're losing. It helps to prevent the last part of that previous sentence.
3:24 - Good dsmash read again.
3:29 - You're being spot-dodge happy. She ftilts your shield and you spot-dodge
after the fact (again). This time she punishes that totally unnecessary dodge with a jab.
3:40 - You pummel her just once below 50%, and what happens? She breaks out! Seriously, do not pummel your opponents when you grab them until they're decently high in %'s. You're missing out on your punishes. I haven't seen you perform a single CG for over a
minute and a half (since
1:50)!
3:41 - Oh man, the music REALLY matches the mood now! DESPERATION IN FULL EFFECT!

Sorry, I really like this music, even though the YT vid is taking away from the quality.
3:49 - After you saw Peach going for the usmash, you could have cancelled the upB and gone for the ledge.
4:00 - Y U no want to chaingrab?!? You're losing badly now!
4:02 - Wow, that abrupt music change was.......distracting...
4:05 - Dthrow > ftilt. Don't you forget about it!
4:06 - Great spot-dodge catch with that dash attack (DA)!
4:10 - Why didn't you edgeguard her this aggressively for the entire match instead of running back and forth? 'Clutch plays' are cool, but it's so much better when you play at your best throughout the entire match.
4:13 - You knocked her out of her float with those bairs. It was risky but I would have let go of the ledge and kicked her again. It most probably would have stuffed that fair she tried to knock you off the ledge with and it would have been
extremely beneficial to you because it would have knocked her out of her DJ (which she used to try to fair you). Then you could have just punished her solo umbrella recovery (child's play).
4:25 - You got scared, which caused you to roll into that fsmash. Stay calm and play normally.
Well, better luck next time! That was a really close match and I could have seen it going either way at the end, tbh. I think the one thing that hurt you the most was the lack of capitalization on your grabs. Of course, I'm referring to the extreme lack of CGs and CG follow-ups. Other than that, I just think you need to get used to the concept of DDD instilling fear in his opponents and taking advantage of the preemptive actions that many people will take to avoid his grab and bair. Also, don't forget that you can use Inhale to cover your landing if you need it. Other than those things, that was a pretty good match for a new DDD. Good stuff! I know you'll do a lot better next time!
Edit: Come to think of it, I NEVER saw you use dtilt, not even once. I highly recommend D3's dtilt, especially at neutral when you're afraid that ftilt just isn't safe enough. It's strong (can kill at high %'s when fresh), and it has fairly low startup and lag. It's faster than ftilt and around the same speed as utilt with considerably more horizontal range. I believe the move can randomly trip the opponent too, so make sure to use it. It's also pretty decent as an edgeguarding tool, especially if your opponent likes to come in slightly above the ledge.