In Gen VI, starters were 4x weak to the Pokemon that have a type advantage.

So, for example, Greninja was 4x weak to the type combination of Grass/Fighting and so on.

Assuming the starters' final evolutions are Grass/Steel, Fire/Dark, and Water/Fairy, there rises a slight problem:

>Grass/Steel is 4x effective to Water/Fairy
>Water/Fairy is 4x effective to Fire/Dark
But, there's a problem here.
>Fire/Dark is only 2x effective to Grass/Steel

The only way to balance this?

>Fire/Fighting is 4x effective to Grass/Steel
>Grass/Steel is 4x effective to Water/Fairy
>Water/Fairy is 4x effective to Fire/Fighting

it's happening again isn't it