IMO, the Great Axe of Sharpness>Lightbringer Greatsword>Greatsword of Doom. GAoS is +2 to hit, +2 damage, and an additional die (d10) of lightning damage on top of that. LB greatsword is +1 to hit and an additional die (d8) of radiant damage on top of that. All the doomblades have no bonus to hit, don't count as magical weapons (I think), and do bleeding damage over subsequent rounds. While the bleeding damage can add up over time, enemies shouldn't live more than a round or two once you started focusing on one in particular anyhow. I usually get the ingredients to make the LB greatsword first, make that, and then have my 2H pally user carry it until after Coparann. I don't bother with the doom blades at all. Note that a great axe does 1d12 of damage, average 6.5. A greatsword does 2d6, average 7. So but the greataxe has a better to hit bonus, +2 to damage, and a better die of additional damage (d10 averages 5.5, where d8 average 4.5), I would prefer a greatsword, but not given the options in Solasta. The LB greatsword works great though against enemies who are susceptible to radiant damage or immune to lightning.