I think everybody overestimates how lethal GURPS is. I've only seen like two PC deaths over several campaigns which featured the tactical combat rules and plenty of opportunities to employ them. Old School D&D is deadlier than GURPS by magnitudes.
@Provinto one big thing seems to be low-tech healing by the rules. But yeah, The lethality is a lot higher if the PC doesn't use things like retreating defenses and all-out defense. Though another thing in low-tech games is just how heavy good armor is. And expensive, especially if you're using the 80/20 starting money rule.
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