The Water Horse is in a bit of an awkward position because he is too small to be considered a Kaiju but too large to be considered a Giant Monster. As a result this creature doesn’t seem to have a lot of fans. It has a lot of raw power, but that won’t mean much against Donatello’s large arsenal of tech. He’s also a close combat master so that’s another feather in his cap. He can take his time and will win this match without too much effort. Donatello wins.