Fantasy creatures are great in general, because they can have such creative designs
But the first thing that popped into my head were aliens, just because of Halo/destiny
They're different enough from humans that you don't have to feel super crappy for destroying them, they can have justifiably different abilities, movement, weapons and weaknesses, and they can explode with whatever crazy effects you can think of
You did indeed stab me in the back. However, you are only level one, whilst I am level 50. That means I should remain uninjured.