it is no surprise that the rebellious side of people would kick in when it comes to Magikrap. Magikarp in pokemon is portayed as the most useless and incompetent pokemon in the history of pokemon.
Infact, Engadget quoted the in-game Pokemon Encyclopedia's about Magikrap and found that it uses words such as, "Worthless. Pathetic. Horribly Weak. Virtually useless". Quite honestly, it somewhat is. Magikarp is a useless pokemon and the only reason why people catch it is so it can turn into Gyrados, which is a powerful one.
However, some people go so far as to beat entire pokemon games using just the fish. In fact, the recent released game Pokemon Sun and Moon was beaten entirely by a player using just a Magikarp. But how did they do it?
Well, just like every great magic trick takes a lot of preparation behind the scenes, it also requires a ton for a Magikarp to win against any foe. For instance, in Pokemon, there are alterations one can make to their pokemon. First, they can give them a specific set of moves which are compatible and natural with the Pokemon.
Second, they can give their Pokemon a held item which gives it certain advantages. In Magikarp's case, they give it an item which keeps it from evolving into a Gyrados. Third, there are many in-match items which can be used. Things such as health restores, move restores, defense upgrades, revives, etc.
The Magikarp is brought up to a high level and many items are stocked up. Kotaku also showed a video where one kept using the X Defense item to make sure the Magikarp took as little damage as possible. Then, a certain moveset is created.
Flail is a move that Magikarp can learn. It says that the lesser health the pokemon has, the more damage it will do. At 1% HP it is at its maximum output. It is then brought down to a very small amount of health but is kept alive using defense moves and health restores.
It then uses Flail to beat nearly every pokemon in the game. However, Ghost type pokemon does not take damage from Flail since it is a Normal Type attack. This is where struggle comes in. Once a pokemon has no more move PP (Power) left, it then uses struggle.
Struggle damages ghost type pokemon and so essentially, Magikrap can beat any pokemon game.