You need a Critical Stage of 5. This can be accomplished by doing all of the following:
- Using a move with a high critical hit ratio.
- Use Focus Energy.
- Hold a Scope Lens.
- Have Super Luck as an ability.
Or, if you're in Wonder Launcher:
- Use Dire Hit 3.
- Use Focus Energy.
Basically, get the chances to add up to 5 using the red chart here. Note that the effects of Lansat Berry, Focus Energy, and Dire Hit do not stack.