Magikarp

Team Benefit

Magikarp is one of the fastest NU-tiered NFEs, on par with Feebas. Although Magikarp's Bounce can hit Grass-type Pokemon for super-effective damage, Pokemon that otherwise would render it answerless, it still needs team support, as anything Bounce hits that isn't a super-effective hit will likely be a 2HKO. Threatening Magikarp are Pichu, Poliwag, Turtwig, Bulbasaur and Chikorita, who all carry super-effective hits. One's own Grass-type can combat this, notably Turtwig, who can set-up on a switch, and provides sturdy defenses. Chikorita can do the same, as well as set up Light Screen to give Magikarp a better chance at taking hits, although Bounce wastes one of the screen turns.

Counters

Magikarp's main tactic is to use Choice Band to increase its very low Attacking power, so once its attack is defined, it becomes much easier to counter. Shinx is resistant to Bounce, and can attack Magikarp with Thunder Fang or Thunderbolt for a usual OHKO when factoring in Stealth Rock. Pichu is in a same situation, although its Defense isn't as high and doesn't appreciate being paralyzed. Almost any bulky Pokemon can give Magikarp a hard time, as even with a Choice Band, frail Pokemon are normally 2HKOed. If Magikarp uses Tackle, Turtwig and Bulbasaur can completely wall it, and shut it down with almost any Grass attack. Squirtle has plenty of Defense to ward off most of Magikarp's attacks and can hit with Brick Break, although it won't enjoy the paralysis risk that comes with Bounce as much.