「The Battle Cats」
IOSのストアでは、このように登録されています。
This is the actual name that is used by the game creators in the English App store on IOS.
「Nyanko Great War」
2つ目は直接的な翻訳です。
Great warとすることで作品の雰囲気をより出せると思います。
This is more of a direct translation of the game name. Nyanko stays the same, but "Great war" indicates what kind of setting the game has.
にゃんこを無理に英訳しようとすると、Kittyと言えますが、このままの方が自然です。名前は無理に英訳する必要はありません。
You could also translate Nyanko - directly into "Kitty" which is a childish term for cat or kitten. In this case the whole direct translation of the game name would be "Great Kitty War" or "Great war of the Kitty's" but just like you wouldn't translate certain names in Japanese to English like a person's name, the name "Nyanko" is best not translated here.
I hope this will help you.
お役に立てば嬉しいです