Help me find a way to teach him

Is this a power-thing for the 11 year old? What is his home life like? Is he bullied there? I have an 11 yo nephew and he is VERY gentle with his 2 yo cousin who he sees 1 or 2x a year. I agree that 11 is old enough to know better, but I also think he is acting out some of his own issues. Does he need to feel babied or loved? I don't think punishment and reducing privileges will have much affect. Would 1-1 time with your family (either you or DH) without the 2 yo help? You do, of course, need to protect the 2 year old first and foremost. Highly supervised play is needed - maybe stories, music or puppet shows where you are all together. This may not be what you had in mind (you're already raising one kid and don't need another), so perhaps limit his coming over if you can't devote complete attention to playing with both of them. (I don't mean that to be snarky - it just looks like the situation demands MORE attention than if the 2 yo were alone with you, and that could be draining.)

Where are you whgen these things are happening. I think your 2 year old (for his protection) and the 11 (who needs guidence on how to play with 2 year olds) should be withint arms reach whenever they are together. under no circumstance should either of them be left alone. If your nephew is crying out for attention he wil get it. If he just doesn't relise this is not a good way to playhe will get that. Your two year old will be protected while developing a strong relationship with his cousin.

I see them everyday for several hours. Mom is on complete bed red with a difficult preganacy, dad is working, I was the natural choice for caregive because I have a relationship with both kids already...these are the kids I am helping to raise ( the 11 year old's birht mom is dead and I stepped in at that point to help. ) I try to give the 11 year old as much attention as possible but there are times when he just has to help out....keeping the toddler away from the stove when I am cooking or such...nothing major.
He does this any time he is asked to move C. any time, even if he was just walking past and I or his father say " do us a favour and move C out of the way so I can put this in the oven" ( usually after asking C to move several times)
I can't think of a Natural/logical consquence for this, but we have to do something.

stop asking him to move C. Instead you move C and have him do the cooking. 11 is plenty old enough to move pot from point A to point B.

There is no natrual/ logical consequence for this. You just have to remind him every time. have practice sessions on how to gently move a child while your hands guide his and in the mean time do it yourself. If you can't cook with all the kids there serve something cold. or prepare the meal before he gets there. crock pot or something. or order out.