Does he do things for his father?
I only ask as my DS2 was a little like that when he was 3 - everything was met with a no and he used to taunt and pick on DS1 until DS1 had enough and hit back. He had the patience of a saint most of the time but when he had had enough he used to get dragged into a fight and all hell would break loose.
He is 4.10 yrs now and much better. I gave up on the naughty step as it was just a battle to get him to sit on it and it took so long that we ended up forgetting what he was on there for in the first place!
I found ignoring him if he refused to do something helped. Only good if you have the time to wait it out. Reminders of what he is meant to be doing every couple of minutes but I refused (on a good day anyway) to get drawn into an argument with him.
Count downs worked with DS1 but they just upset DS2 and made him dig his heels in and refuse to do things until you stopped counting down although ironically he generally used to do them if you did stop so I suppose they sort of worked!
The reason I ask about his father is that sometimes it helped to get DH to take over, if he was around and sometimes that helped. He took less liberties with him.
Also praising the little things that he does right helped too.
I think nursery helped too - they used an egg timer to get him to do things as he refused to do them there as well.
However, if you are consistent in your approach I bet you it will be just a phase as my DS2 is pretty good now, a year or so down the line.
Good luck