Is there a good cheap build that can kill all or almost all endgame boss?

[LordManhammer]

You can do the same thing with the Plaguebringer dagger from the LK. Conviction works against poison res as well as elemental res on this mod. The proc from the dagger is enough to kill him even without Conviction if you need to have Salvation up instead. I tested it. Frostmourne is a bit faster is all