It might be a little harsh to classify a Magikarp as a baddie by traditional standards, but all Pokemon should be classed as such in the eyes of the imperial hunter you must become to achieve the singular motive of "catching them all." You cannot catch a predator without recognising them as your enemy, even when their only attack is basically to look like they're dying having been removed from their bowl. Magikarp might evolve impressively, but up until that point, it is no more than a space filler in your Pokedeck, an actual fish out of water with the same fighting ability, and a move set limited to the laughably ineffectual Splash. Actually choosing a Magikarp to fight for you is suicide, since it's the equivalent of pitting a goldfish against an Apache helicopter (regardless of who the foe is,) but fighting against one, should the urge for a merciless and spectacular reign of death appeal to you, is just tragic. If you genuinely want to experience how rubbish Magikarp is as a foe, go now and find a goldfish - take it out of its life-giving water and punch it as hard as you can in the face. Same thing.
Actually choosing a Magikarp to fight for you is suicide, since it's the equivalent of pitting a goldfish against an Apache helicopter (regardless of who the foe is,) but fighting against one, should the urge for a merciless and spectacular reign of death appeal to you, is just tragic. If you genuinely want to experience how rubbish Magikarp is as a foe, go now and find a goldfish - take it out of its life-giving water and punch it as hard as you can in the face. Same thing.