A renegade player can convince Mordin that the Genophage Cure isn't worth it, and he'll be cool with it and you'll get both Salarian Aide and Wreave's Krogan help. I write that as I couldn't live with my decision on a renegade run.
As a renegade player if you choose and kill Wrex in the first game and in the second convince Mordin the Krogan research isn't worth saving, you can convince him at the purifier as both Eve and Wrex are dead and the future of Krogan with Wreave is just repeating the same cycle as before... so he accepts your argument and you assign him to the crucible project instead
The choice is a decision between two good characters, but if you decided to go full renegade on that choice, it is a choice betwen killing one character early over having to live with the consequence of directly killing two that know you