Who would win 

Enel from one piece 

or 

Pikachu

my opinion: this is hard to say but if we are talking physical combat enel stomps cause a pikachu with lightning rod can absorb the lightning enel fires but it still won't be good when you count physical combat like he was able to take on luffy and hold his own espite luffy being made of rubber but he's able to also heat up his trident to do some good amount of damage and i'd give it to enel.