Only losers uses hacked Pokemon.
I played against a Pokemon X/Y player from Japan the other day who was using an obviously hacked Shiny Mega Kangaskhan.
I had my Gale Wings (grants +1 priority to Flying moves) Talonflame use Brave Bird (Flying move) against my opponents weak Mega Kangaskhan that previously used Power-Up Punch, but my opponents Sucker Punch (+1 priority move) ended up outspeeding and knocking out my Talonflame, which resulted in me losing the match.
The highest Speed that Mega Kangaskhan can reach at level 50 is 167. My Talonflame has a Speed rating of 195, which is the highest possible Speed that Pokemon can reach without a Choice Scarf.
Sucker Punch is supposed to fail if a faster opponent uses a +1 or faster priority move. That proves my opponent was using a hacked Mega Kangaskhan.
The fact that Nintendo allows abnormal Pokemon in Free Battle matches is embarrassing. That game can be easily patched to ban such Pokemon from those matches.
Players that uses hacked Pokemon in Free Battle are pathetic. What's the use in playing Pokemon if you virtually guarantee a win?