Hey K-9. I like your usename...its awesome =P
Match 1: DDD
First off, watch your skull bashing. Its really predicatable and you got punished three times with it against DDD. Its tempting to use it for a recovery, but double jump and QA will get you back to the stage almost every time. Use an uncharged skull bash if you are really high up, or a fully charged one to go under the stage to the other side. If you use it parallel to the stage, it can get intercepted easily, especially by characters with powerful/high priority aerials. Just be careful of when you use skullbash.
DDD's backthrow does 16%, the most damaging throw in the game. You got shieldgrabbed way too much. You can grabbed about 10 times (estimate) in that game * 13% per bthrow (account for move decay) = 130%, just from getting shield grabbed. I know its extremely hard to not get shieldgrabbed by DDD, since he has an absurdly long grab range, but there are two ways to avoid getting shield grabbed. You have to perfectly space a fair. If you fair and it hits his shield, try to use pikachu's great aerial mobility to back out of his grab range. You can also do a cross up fair, which is when you fair, but you go through DDD and land behind him. Be sure to DI up on DDD's dthrow. I think you should be able to jump out of it to avoid punishment, or at the very least, you will be able to tech the dthrow to avoid his followups.
You need to Chaingrab DDD more. Nice combo's.
Match 2: Sonic
Skull Bash again...
Nice thunder setup and kills. =)
I like your edge taunt thing.
More chaingrabbing.
Work on your edgeguarding. I'm not sure how comfortable you are offstage, but pikachu has many offstage options. If you timid offstage, just jump and shoot tjolts and edgehog. If your slightly more daring, multiple thunderwalls do really well. If you are really comfortable off stage, you should chase them down and either uair to steal their second jump or nair for the kill, then QA back.
Match 3: Sonic
Ah, better edgeguarding. That's what I like to see!
You almost got punished on the last stock while using Skull bash.
Work on your combos a bit. You pulled off some really sick combos on DDD, but I didn't see you combo sonic any.
Overall:
Use less skull bash and watch out for getting shield grabbed (especially against DDD). You need to chaingrab more, especially after your opponent respawns. CG's are a free 50-60% of damage. 50% * 3 stocks =150% total = 1 stock. CG's basically remove one complete stock from your opponent...good stuff. You need to edgeguard your opponent more. Do more combos.
I think that's it. I'm very impressed withi your pikachu. Good stuff K-9!