Hmm, well. I don't know of any specific suggestions, but I think I'd try and keep it within the realms of, um... well, fusion would be powerful enough to, say, flip some large vehicles pretty easily. Full-on summon would probably be pretty dangerous strength-wise.

As I've established with Artemis, gods are strong. Since she's weak in terms of strength and can still pull a bow back hard enough to send the arrow she fires through a wall. So I'd suggest maybe strong enough to take on other gods in hand-to-hand(which probably would be a thing for most combat-leaning gods in this setting in one way or another, even if it's a hit-and-run kind of style).

Though keep in mind that other summons can fight gods(except the most powerful which probably won't be accepted unless the signup is very good).