Wow. You know, i've been playing Pikachu for 2 years now i and thus am the best in my region. I felt like checking smashboards for some random reason even though I haven't been on here for a year. I find it utterly hillarious how people still have questions about the fundemental problem of pikachu after like 3 years from the games release. I figure you're not a pika main nor have you looked into any of the information that is available to you on youtube. If you had done some research you'd find great guides from esam.
That said, i can give you an idea of how to kill with pika other than up throw thunder.
Obviously Pika is awesome at gimping so that should be your main tool to take stocks
At high percent (150%) you can get f-tilt at the ledge.
fastfall fair -> upsmash is true for light characters.
nair at the ledge can kill ove rlike 110%. if you read a normal get up, its easy to hit.
jablock setups are also pretty effective though i wont go into that since that would take way too long.
i hope i was able to give you some insights on other killing options