>I get the idea that counters don't have to be items.
>
>>> 2) Overwhelms existing counters, if any. There is little to nothing an opponent can do to neutralize it, even if they know in advance that it is coming. Countertactics have to be evaluated on availability, potency, and the existence of counter-counter-tactics.


I believe 'counter' was meant in strategy and class abilities as well as item use. For example, fly can counter trip, but ground control can counter flight. So, strategically many things can be nullified, ignored, or even used against you. If flight always made sure you'd never be affected by trip, earthquake, quicksand, and so on, it could be considered overpowered. It isn't a guarantee, so it's not.