As strange as it sounds, I can't help but feel that Theá and Torrential's relationship is somewhat strained. Possibly with other alicorns as well.

I honestly see Torrential as an alicorn that encountered his own nightmare form very shortly after the dawn of creation and instead of forcing it down and turning it into a completely separate being he embraced and merged with it. Sometimes the world is a dark, violent and angry place and Torrential accepts that part of himself fully; Thus why he can go from being a kindly father figure to a complete and utterly remorseless sadist when the situation calls for it.

It also doesn't help that Theá tends to deal with her enemies as accurately as an arrow through the eye from three hundred or more yards where Torrential's way of dealing with his enemies tends to maximize collateral damage and civilian casualties.