With 15 str, I recommend the Military Cleaver, Broad One Handed Battle Axe, Military Pick or Military Hammer, in this order. You can also try the Steel Pick, but for me, it was too short. Dito for Warhammer. If you want a sword with stab, try the Langes Messer. You shouldn't go below 33 cut damage with only 5 PS, though, so I would rule the other swords out...except maybe the Arabian Cavalry, although it is a bit of a niche sword (you must play out its surprising reach).