Anti Ataxx (where capturing is compulvasory over other moves) or Ataxx 9x9(more time to prepare for the battle) or an Ataxx variant where you may only clone orthogonally, and jump L's or diagonally.
(hide) If you want to play a game with an opponent of a similar level, you can define a required BKR range for a new game invitation. Then nobody with a BKR outside this range will be able to see/accept it. (Katechka) (show all tips)