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False Swipe isn't an offensive move and definitely isn't something you should use in competitive battling. It's used for catching Pokemon due to its nature of leaving the foe with 1 HP. You use False Swipe when a pokemon you want to catch has very little HP, so you can bring it down to 1.
Yeah, like somebody said above, you shouldnt use it if you plan on battling. Use it, if you plan on catching a wild pokemon that you cant afford killing.