Give the Pokémon the item Focus Sash so it could survive the other Pokémon's first attack. Or, use a pokemon with sturdy. After the attack, use Endeavor to lower the other Pokémon's HP to 1. Then use Quick Attack to defeat it.
Many trainers lose a Pokémon battle due to this tactic and many people want to know how to combat this cunning tactic. To beat it, either use a poison-inducing move (eg.Toxic), then use another move or use a multi-hit move (eg.Double Hit) or use a ghost type Pokémon.
Ghost pokémon are immune to this tactic as both Endeavor and Quick Attack will not affect them.
Another technique is to start with a Pokémon which creates damaging weather effects (eg Tyranitar) and to teach it Dig. On the first move Tyranitar will avoid the Endeavor attack and the opponent will be damaged by the sandstorm, and then knocked out by Dig on the second turn.
Alternatively, you could teach your own pokémon Quick Attack and beat your opponent at his or her own game.
Challenge Marriland in a Wi-Fi battle you will find out that his Rattata (Fear) who used to be Lv. 1, is now Lv.100 so it cannot use the F.E.A.R. strategy. Or, use another Lv. 1 against it, and just go on. Make sure you have a lower HP than your opponent. It's tough, but it will work!