None in this era anyway. The HOMM AI was reasonably good at what it did, enough that rookie-to-some-time-invested players would struggle, while experienced players could trash it. That's pretty similar to EU IV.
If you count RTS as competitors, the AI has a distinctive advantage there as you've no diplomacy (an AI weakness when there is diplomacy) and lots of micro pressure (theoretically an insurmountable AI advantage in terms of potential raw #inputs/time, though it does have to choose good actions). Top notch pros in Sc2 can get a few hundred actions/minute, though how many are useful vs not is debatable. An AI could do many more than that though.
In Total War 2, if you take a nation's last city, despite having a 20 man army capable of capturing a new place to reside they will sit in the open or even on the sea in raiding stance getting attrition until they have few men left, then attack their old city no matter how many men are guarding it...
Steller AI. I want to like that game, but every time I see something like that I quit.