This is why you act as fast as you can. Don't give them time to remove evidence. And bug them from the start.
But the no evidence thing doesn't make sense. On one hand, the evil guy is reasonably competent at erasing traces. On the other hand, that shouldn't be enough. There's way too much power, both politically and physical power, to not be able to just end him.
At last someone who isn't outright complaining about MC being a God and not killing the Pig Marquis right away.
As for the plot, politically while MC has a lot of power because of his engagement with the Princess & the Knight General, but MC (who is currently a Count) is still lower ranked than that Pig Marquis, so by law he can't do anything without proof.
As for his strength, i know that MC is OP, but he is only that in his powers not his capacity to handle politics.
And not everything can be handled with just strength.
Yeah he is basically a God, but that power is primarily for him to fight natural disasters or the evil god. Not some lowlife scum (it's like asking to use a mega crane to open a door).
Well, in the end i guess the "That" the Marquis mentioned might be related to a Fragment of the Evil God, which would allow MC to go full force after him.