I have come to a standstill in the Cheydinhal Mission: Corruption and Conscience.

I have completed all the steps up to finding Aldos Othran and following him to his house - once there he stands and does nothing. He is suppopsed to kill the guard. Anyone know of a fix or a way to mark this step/quest as complete?
Thanks

Does he talk with the guard at all?

If he did do the dialogue with the guard but nothing happened after that, it happened to me too, and I found out Reneer's Guard Overhaul was the problem. The most straightforward way to complete the quest stage is is simply killing Aldos - bring up the console, click at him, type "kill" and press enter. You could also go through the quest with RGO disabled... supposing you even have it.

If that's not your problem, I have no idea.

And BTW, the guard kills him, not the other way around

I had suspect that the Guard Overhaul Mod was the problem. I do not think he has spoken to the guard but will try the fix you suggest, thanks