Which level 7 creature is the best, and why?

I can demonstrate. Create a map in the editor, place the specified units, conduct a series of 1-on-1 battles between Death Knights, Titans, and Archangels, then upload it, and maybe you'll reconsider your point of view... :)

In general, I created a video, and I'll upload it tomorrow. It will be in the sav format; rename it to avi. The battle will be between an Archdevil, first against a Titan, and then against a Black Dragon. The quality isn't great, but everything is visible, albeit slowly. I'll say right away that I play fairly, without any cheats, etc. Everything is visible there.