If you want to win final boss with human race, here is the trick, untill you destroy his castle send archangels with 3 canons and 3 wizards in his back, after you destroy the castle send only red dragons with 3 + 3 canons, wizards the boss won't slam the ground vs red dragons and the conons + wizards will kill al the minions units.
Regards,
rate up to keep it alive