Leyrann
Deity
I have a battering ram next to an enemy capital -- it prob has medieval or rennaisance walls, strenght of 63-- and my sword dies attacking it... negligible damage to walls. WTH. Civ6 is so frustrating. Shouldn't it take down the wall in one hit and survive, due to the ram? If I'm doing something wrong... will a siege tower do any better? Thanks...
The damage your swordsman takes and the damage it deals to the city itself does not change. The only difference is that it deals additional damage to the walls - normally it deals reduced damage to those, now it doesn't.
Anyways, attacking something with 63 strength with something with 36 strength is not a good idea, no matter what. That's a strength different of 27, which can indeed be a one-hit kill (it's possible from 26 strength difference on, and happens 50% of the cases at 30 strength difference). Use bombards (catapults would barely dent a city with 63 defense) or musketmen. Knights and Crossbowmen could work too, but will deal little damage, and in the case of knights will take significant damage in return (even musketmen will if they don't have the Urban Warfare promotion). If you don't have those units, you'll just have to back off and wait until you do have them.
Edit: Additional calculation for the swordsman attacking the city, assuming medieval walls (80 fortification health), your swordsman, with 27 strength less than the city, will likely deal about 12 damage normally (rough estimate; with 30 difference it deals 10 on average). This is reduced to 1, maybe 2, if you do not have a battering ram, but even if you do have a battering ram, 12 dmg on 80 fortification health isn't much. If it's renaissance walls (120 fortification health) it's even less.