UNPOPULAR OPINION: CHAMPIONS DONT NEED COUNTERS...

..IF they have clear built counterPLAY.

A counter is a champion who's kit ignores/ stifles the strengths of, or takes advantage of the weaknesses of another champion. This keeps down the win rate of powerful champions since they have disadvantaged matchups, or raises the winrate of weak champions by giving them advantaged matchups. There is nothing inherently wrong with this, and in fact it is likely healthy for the game to some extent.

That said, a champion can also have their winrate lowered without nerfing a champion's power by giving them built in counterplay. Champions who prefer to fight at certain ranges, are gated by key cooldowns, or rely on special mechanics to be effective all give more skilled players windows by which to take advantage of mistakes or find better openings to use their own power spikes. A champion with these kinda of qualities will generally not need stat or kit checks to mitigate their effectiveness as they have a universal counter built in: a skill check.

It is important though that these weaknesses are clearly discernable, or a champion can appear to have none at all to less skilled players.