In 5e, a crit doubles the damage dice you roll. So if your weapon deals 1d8+stat, your crit will deal 2d8+stat. It's possible to roll two 1's on a crit and deal very little damage.
Thanks, that explains it. So a 2d6 weapon will double to 4d6?
What weapon did you use? Slash or blunt damage? did you try other weapons with different damage effects? A weapon is tool and some enemys need different tools to be removed.
Think about the minotaur's in the under dark with slash and pierce resistance amulette.
well here is also the problem you did not have a helmet that protects from crits!!!
Wait, I know that's what helmets do in BG1/2 but do they still do that in BG3? The one single helmet I've found so far mentions a + to dex saves I think.