Which level 7 creature is the best, and why?

Listen, Zhenya, you have such a funny way of expressing yourself... I mean this: you say that a black dragon can easily defeat an archangel – that's interesting, but how? Have you tested it yourself? For example, create a map in the editor and see what happens, how, and at what cost?
Furthermore, you write that archangels will go first, morale, etc. – it's pointless to argue with that, but isn't complete immunity to magic weaker? – I don't think so.
Again, I disagree – game situations can vary ;)

Greetings to all!
to Ley: you are right about the situations, it all depends on chance.
I just checked – I was surprised, the dragon loses :) – this is another argument in favor of the archangel....
And here's another thing: immunity isn't that great – you can't even cast a blessing, and the larger the army, the less combat skills matter.

battle of Edric 0 0 1 1 (1 archangel) VS Solmyr 0 0 1 1 (1 black dragon)
Turn 1: Archangel deals 62 damage – black dragon retaliates with 40 + attacks for 42, archangel retaliates with 62
Total result of the first turn: archangel 168 HP, black dragon 176 HP
Turn 2: archangel 62, black dragon retaliates with 35 + attacks for 39, archangel retaliates with 62
The result is 94 archangel vs 52 black dragon
That is, you need to cast a maximum of 2 lightning bolts with 50 damage each, or 1 with 100 damage, to defeat the archangel, otherwise....:smile02:
P.S. Moreover, the archangel has a chance to move twice without taking damage (+2 morale vs +1 for the black dragon)
And the more creatures there are, the stronger the lightning bolt needs to be...