We have another advanced Pokemon X and Y guide for you trainers! This is another way to breed Perfect IVs. This won’t be the ideal method for everyone, but it will remove the luck factor from breeding, and you will know exactly what stats your offspring Pokemon will inherit.
Before proceeding below, you need to acquaint yourself with the conventional Perfect IV method. If you are starting out, you will be better off using one of those methods. However, if you have gone through several generations of IV Pokemon and have been having trouble getting that Perfect IV bred, this is the guide for you.
You need a male and female Magicarp and the Destiny Knot.
Go to the Battle Institute in Lumiose City to find out their stats, and write them down. If they share one or more stat, you’ll want to get rid of one and try to make a pairing without matches. Once that’s taken care of, put them into the daycare with a Destiny Knot.
Decline the first egg, save, accept the next egg and hatch that. Then go to the Battle Institute again and check its stats. Now, you can cross reference the offspring’s stats with its parents and figure out which stats came from which parent.
What is the significance of this? Essentially, you can now predict which stats will be inherited from which parent. Prior to this, Pokemon breeders literally had no control over this, in spite of narrowing down practically all of the other factors and figuring out how to control them. Now, you don’t have to worry about chance; you will get your 1st Perfect IV Pokemon! But there’s a catch.
The catch is you will need to have a set of parents prepared in advance that match the patterns set by the Magikarp you started with. If you do, you can guarantee the Pokemon those parents have will be a Perfect IV at birth. This raises a new problem, of course: raising the parents to match that combination.
And to do that, what you will need is several IV Pokemon prepared in advance. If you were so dedicated that you had multiple potential parents in the wing, then this technique is perfect? If not, you will either have to grow your Pokemon collection – or, leave this part up to chance.
Assuming you have a perfect match, reset the game by pressing L+R+Start+Select all at once. Switch the Magikarps for the parents you have in mind and repeat to replicate the results.
Source: Reddit