Welcome to Smogon! Take a moment to read the Introduction to Smogon for a run-down on everything Smogon, and make sure you take some time to read the global rules.
Here is the Team I made for season 13. It uses Scarf Entei to surprise the opponent and burn his mons. Entei to C!
:entei: :porygon2: :mimikyu: :primarina: :thundurus: :rillaboom:
Pokepaste
Blog Post
won in 2 ggs against RoyalReloaded
https://replay.pokemonshowdown.com/gen8battlestadiumsingles-1019801986
https://replay.pokemonshowdown.com/gen8battlestadiumsingles-1019803344
He also had Entei in his Top 30, but no Charizard X :D
Not sure about Tapu Koko though, I think it's about equally viable as Gyarados or Snorlax or Hippodown which are also A+