Overlord III

Both isekai animes have OP characters as their main, and also focuses on world-building while leading an army. 

Stories are about war that is brewing. Lots of drama that is tied to war: suffering, sadness etc There is good amount of interactions between both sides of conflict. Soldiers of opposite side are likeable even though they arent human. 

Antihero / (somewhat) Evil Protagonist, medieval times with magic / fantasy setting, a unique twist on a common setting. Both provide gore and target an adult audience. 

Both of the characters use their brain, and while in Log Horizon the MC may not be OP, he is able to secure a lot of power just by taking advantage of the game he is trapped in. 

The same MC whom were anti heroes who have a harem and doesn't know what to do with it and the same MC whom has demon like powers.  

Both have OP non-human MC who doesn't really care about humans, but about their own people who are different kinds of monsters. Both are parts of franchises and have similar developments in terms of their own stories - one becomes a Demon Lord and the other one shows off his ''true strength'' (more like just a part of it) to humans. They both decided to go into a war with human nations to make their nation or to strengthen their nation.