Depends solely on pokemon. Physical sweepers I prefer Adamant and Jolly (slow (Below <70) Ada, Others Jolly) Same for Special sweepers but with Timid and Modest. special walls Careful and calm. (Depending on attack stats, Spiritomb is Careful, Regice Calm) Same to Physical Tanks with Impish an Bold. For Mixed I use Naive or Hasty. Scarfers usually Jolly/Timid, sometimes Adamant/Modest. Mixed if they are fast enough Rash, mild, Lonel and Naughty. Slow Pokemon with Gyro Ball or Pokemon who are made to withstand Gyro Ball the option is Sassy or Relaxed. There are some Special cases: TyraniBoah can use Quiet, Swampert Brave and etc.
There is no "Favourite! nature for me.
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By St. Jimmy.
If you have any problems with breeding, Egg moves, IV:s or EV:s, you can ask me. Feel free to ask other things related to competive battling.