> A submarine is a hard counter to an aircraft carrier -- that's why we put sub-hunters on carriers and surround them with anti-sub ships.

In video games that's true. But aircraft carriers can have sonar-equipped helicopters take out submarines.

Aircraft carriers are also faster than submarines, so in practice, I'm not sure if submarines can practically chase down an aircraft carrier and actually disable them.

Honestly, I'm willing to bet that most of those Destroyers in a Carrier-strike group are there to shoot down cruise missiles (which are probably a modern, hard counter to Carriers. Cruise missiles are very expensive, but Carriers are even more expensive).

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"Hard Counters" exist in the real world, and they're far simpler than you think.

A tank is the "Hard Counter" to small arms fire and even small-autocannon (30mm or less) fire. Modern tanks are immune to such weaponry. No matter how many AK-47s you send towards a tank, they will all die.

You need to switch out your infantry loadout: you need to start sending RPGs / Missiles / IEDs if you want your infantry to have a chance vs tanks.

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Historically, an A10 or Helicopter was the "Hard Counter" to a tank. Tank guns have extreme difficulty aiming that high (tanks are designed to take out ground targets), and a tank's 130mm cannons are powerful: but A10 / Helicopters will dodge most of those shots due to the low-rate of fire.

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The concept of "Hard Counters" leads to the modern battlefield concept of "Combined Arms". You should never send a platoon of tanks by themselves to face an enemy (they'd just die against their helicopters). You instead, combine different arms together to form one group: send a tank with infantry + AA guns, so that you can face all sorts of different enemies as a team.

With "combined arms", you negate your weaknesses somewhat.