What can an attacker who controls majority or all of the full nodes do? What happens when a strong attacker has control of majority or all of the full nodes?  

What damage can he do and would they be reversible?
Here is an additional answer about what you can do if you control all fully validating nodes (but not necessarily all nodes that don't validate):

Anything

Bitcoin's security rests on auditing by full nodes. It is directly what prevents them from accepting fraudulent payments, and indirectly what makes it uneconomical for miners to produce invalid blocks (which in turn could be used to defraud non-validating clients).

If you have control over all fully validating nodes, you can effectively set the protocol rules at will. Including but not limited to theft and printing money out of thin air (beyond what the subsidy schedule currently permits).