Requirements:
None.

Method:
The achievement description is self-explanatory.
Usually this would mean I wouldn't be writing a guide for this achievement.

However this achievement is positively glitched.
For me the achievement popped up when I won a showdown with two pairs.
I am under the impression that one does not have to meet the described requirements. My impression is that it is sufficient to play the game a lot. After an undetermined number of showdowns the achievement will pop up.

Important Notes:
Meeting the actual requirements would require a lot of luck.

Recommendations
Keep playing and winning showdowns.