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TBH I play no particular tier the most. I would argue that Gen 7 Ubers is my best format, but I also am getting fairly good with UU, RU, OU, as well as NU and PU to an extent. For example, I made a Gen 7 Ubers team that I named "King Ramses' Curse" and I think it is BY FAR my best team period. https://pokepast.es/2c6cdda986940306
Land's Wrath is a great counter against Fire and Poison and Electric dual types that think they can pull off a super effective Dragon attack on you. Everyone is expecting Thousand Arrows when I try it on Zygarde, so that's just my logic.