On large-scale maps, where a game lasts for about 30-40 months, Ancient Wonders are dominant. Personally, I managed to defeat around 2000 Archangels and 500 Dreadnoughts with minimal intervention from external forces, using Ancient Wonders, with a slight difference in Attack and Defense stats between the heroes.
Overall, I prefer the top four creatures – Black Dragon, Titan, Archangel, and Ancient Wonder – each of them can be the best under certain conditions.
The remaining level 7 creatures, in my opinion, are all inferior to the ones listed above.