2nd build looks pretty decent. Well, giving honest words, Mordekaiser needs offense earlier into the game, and defense at late game. So, you should always get a decent burst damage before building your armors and resistances.

+1 for your second build, good luck improving your guide

Very nice guide, but i like maxing mace of spades and siphon of destruction first. It makes it easier to farm and get first blood. I will give you a tip when you're laning and are low on health use ulti on them it will heal you a bit.
So good job.
+1

i would change sunfire for zhonya and FoN for rylais and instead of rushing for gunblade after WotA buy hextech revolver and get gunblade after abyssal scepter you should also add regrowth pendant to your core build instead of amplifying tome, dont get warmog for your second build there are better items for morde

Very nice build, but there are a few things I wanna mention. With 2.1k health, do you really need a force of nature? and you have a nice 200 Mres, but only 90 armor... overall, I liked the build. Good work