Which level 7 creature is the best, and why?

Ley, agree that whoever strikes first has a significant impact. I should say that I haven't tested 100 Chimeras against 100 Archons, but I will test it today... But for some reason, it seems that whoever strikes first will win.

You have a strange way of expressing yourself... If we reason as you do, then monsters would always win, but the turn priority isn't in their favor, therefore monsters can only strike first in one single case - with Hydras, and even then, only when they are attacking.
To draw a meaningful conclusion, it is necessary to reason based on the speed of the unit, and not on who strikes first - that's silly, IMHO.