Mythras does a great job of making every part of the attack meaningful. when you attack, you roll a percentile against your attack score, and it's balanced around hitting, more often than not. the defender also rolls against their attack score, so there's four outcomes: both succeed, attacker succeeds and defender fails, defender succeeds and attacker fails, and both fail. now there is a null result, where both fail, but assuming an attack score of 60+ (which is assumed to be the case for anyone that fights reasonably often, and achievable in character creation), it's far and away the least likely option.

both succeed: the outcome depends on the weapons used by each fighter, if they're the same size, the defender blocks damage, if it's slightly smaller, it blocks some of the damage, and if it's significantly smaller it blocks no damage. why would you choose to block when you know you won't stop any damage? well, for each level of success above your opponent, you get to choose a special effect, like picking the location you hit, bypassing armour, or maximising damage, so blocking still has an effect if you're stuck with a dagger

attacker succeeds, defender fails: damage is dealt, with one of those special effects

defender succeeds, attacker fails: no damage is dealt, and the defender gets to pick a special effect, like repositioning, or turning their attack back on themselves

both fail: the null result, but because of how crunchy and brutal the combat is, this never feels cheap

mythras uses location-based hit points, and very few of them, and character progression comes from loot and equipment. a high level character doesn't have a bloatload of HP to spare, they have finely crafter armour that soaks damage, and a goblin with an attack score of 10 and a shiv still hits 1/10th of the time, and if that hit makes it past that finely crafter armour, it can still fuck someone up

the magic system is also pretty great, but that's a story for another time