Personalities

There are 22 different poke personalities and these give a stat bonus as well as a stat reduction or sometimes nothing at all to a poke.

Personalities can make a huge difference late game if your trying to min max you stats but it can ruin some potentially too. The idea is to have a -10% on a stat your poke doesn't benefit from.

If the poke is a Physical attack user then ideally having -10% Special attack is perfect and either +10% Speed or Physical attack. In this case cheerful or modest are the best options.

These are the best Personalities for Popular Poke
Arceus: timid

Ho-oh: cheerful or stubborn

Dialga: modest or timid

Palkia: timid or modest

Celebi: timid or cheerful

Zygarde: cheerful or stubborn

Rayquaza: modest or timid

Tornadus: timid

Regigigas: cheerful or stubborn

Regice: timid

Kyurem White: modest or timid

Kyurem Black: cheerful or stubborn

Deoxys: modest or timid

Kyogre: timid

Groudon: cheerful or stubborn

Tapu Lele: Timid

Lunala: Modest or Timid