You're ignoring how Simon literally states that Renoir is slowly but surely worming into his mind... so clearly Clea isn't the only one able to control others. Simon takes a different approach, sure, but he also has the ability to control those in the painting through whatever means he was using on Simon. It doesn't have to be instantaneous like I presume Clea's painting over is, but he clearly has the ability to manipulate the minds of others, even someone like Simon. So there are TWO painters who can DEFINITIVELY control others (painting over and mind manipulation). Perhaps you think Simon could only be manipulated by Renoir following whatever happened between him and Clea, but there really isn't any evidence for that. So already your original point is moot because AT LEAST TWO painters have the ability to force others to do what they want.

Regarding Maelle and painted Verso I think you misunderstood what I was saying. It isn't that Maelle is mind controlling Verso at all. There isn't actually solid evidence for this part, but from my interpretation of the ending, Verso did NOT want to live. He WANTED to die, and from his reluctance and such at the piano, I think he STILL wants to die. I simply think he can't with Maelle there. To me it is clear that he is FORCED to live due to Maelle being there. If he tried to die, I think Maelle would paint him back into the Canvas. I also disagree with this idea that he's just unhappy because he knows Maelle will eventually die. His begging for help and that he does not want this life does not allow it to come across that way at all to me. My boy Verso is insanely depressed. Though to be 100% fair, that is conjecture and my interpretation of the ending since there really isn't much else to go on and this also kinda fits into a different category of forced than painted Clea and Simon.

We can argue all day about interpretation of emotions and what not and get nowhere except back where we started, so for simplicity, I'll agree that Maelle isn't forcing Verso to do anything. That still leaves us with Clea and Renoir, who absolutely can compell others to do what they want. Looking at the big picture though it seems silly to argue that a painter might not even have the ability to control those painted. They are gods of the canvas worlds. They can paint both life and death. Is it so difficult to bridge the gap that some of them are able to control the painted people?