Okay, so I watched all of the videos you posted..
First thing I noticed, as the other guy said as well, you are QACin' a bit too aggressively. Using it aggressively is OK, however when it becomes your approach 4/5times a decent opponent will catch on quick, as can be seen in your videos (especially in the Marth and Falco ones). I'd advise just cutting back on it a bit.
Next thing that I noticed was your lack of using tilts. I saw maybe 3 U-tilts total in all 4 videos combined. By not using tilts you are depriving yourself of 3 quick, good priority attacks that pika has to offer. teach yourself to start using them more; in addition to the obvious direct reasons (such as being able to combo with U-tilt) is the fact that it will further diversify your attack patterns. Making you less predictable.
Item numero three, you use Nair a bit too much. Once again this obviously leads to predictability, however there are a couple more reasons I would advise against this. One of which being that U-air has better priority AND can combo, make use of it (by the way, not using U-air enough is another little problem and adds to your predictability). The next reason is that N-air can be a usefull kill move for Pika, don't lower its knockback so much by using it over and over at lower percents, that is when U-air comes in handy.
Another thing along the same lines is your F-smash usage, use F-tilts to conserve the knockback on the F-smashes for the kill, plus F-tilt is quicker and there were a few times I noticed it would have been a better option for you (D-tilt can replace it as well).
One more minor character specific item I want to bring up is regarding how you fight Falco. As you clearly noticed he was CGing you quite a bit, don't be afraid to get the ******* back. Maybe not CG all the time, but little combos such as Dthrow-->Utilt-->Utilt-->Uair, stuff like that.
Well, that's just my $0.02, do with it what you will. But before I go I want to mention something. I am very glad that you had the balls to post videos of you losing, FAR too many people post winning videos of themselves, I have no idea why, maybe they just don't want to look bad or show off or something. But the best examples to provide for critique are ones in which you lose. Those are the ones where you can more easily see your mistakes and get good advice on how to correct them.
PLEASE, ANYONE ELSE WHO WANTS CRITICISM OF THEIR PIKACHU; FOLLOW THIS EXAMPLE. It is in your own best intrest to do so.
Oh ya, and nice pika. =)
