The archangel waits on the first turn because his speed is higher and the beast's speed doesn't allow it to reach the Arch in 1 turn.
If the Beast goes into defense, the Archangel will do the same. Then the battle won't even start. But the Beast won't win in that case:)

...If the Beast goes into def on the second turn, the archangel also goes into def. And again, the battle won't end if they just stay in def like that.

So, it seems the Beast is probably not destined to win the battle.
But thank you, thanks to you I will know that the beast has at least some chance of a draw in a battle with an archangel;)