This is my advice to a newly minted administrator who is too much of a nice guy to enjoy the power. I would give the same advice to anyone, although this particular administrator is dear unto my heart.
Essentially, he's wondering what to do about a subordinate who just doesn't want to do what he's told to do and what is required of him. I know a lot of people would have no problem with that. In fact, they'd enjoy it. "Great!, a chance to push someone around!" But in this case, we're dealing with a personality that likes cooperation and sees an administrator's job as primarily making things work smoothly. That pleases me. However, it doesn't deal with the important point: what do you do about an employee or subordinate who just won't cooperate?
Speaking as a longtime administrator, even longer time retired, I have to advise that, first and foremost, don't try to be something or someone you aren't. You would be playing a role and you're not a trained actor. Trying to be or do things in a way that is unnatural to you means that you will do them poorly.
The best thing is to approach the situation as it is. That is to say, you have a duty to perform. That duty includes ensuring that this individual performs HIS duty. You don't want to force him to do so, but it is your duty and therefore you will. Explain that to him clearly and simply and follow-up on what results.
If this is enough to convince him to do his duty, problem solved. If it is not, then speak to them again and say, look, my duty requires me to take negative action against you if this continues. I don't want to do that. However, I will do my duty, however reluctantly. So get working and get the job done. Then we will both be happy.
If this fails to convince him, do what the regulations require you to do.
Consider the following two points:
For I am a man under authority, having soldiers under me: and I say to this man, Go, and he goeth; and to another, Come, and he cometh; and to my servant, Do this, and he doeth it.
There was once a very bright young man at my school. He was a good kid who came from a troubled family and home. Unfortunately his background lead him to make some very bad decisions. His teacher was very supportive of him, believing that there was a good center to this youngster and that, given time, she could bring it to the fore. I supported her, but the school counselor and I had a long talk with him. Essentially, I pointed out to him that I also knew he was a good kid. But I added there was no way I could tolerate his excessive behaviors.
I told him I had no desire to see him expelled from school. I thought it would be bad for him and I would think it as a failure of my own ability to reach him. I pointed out how much his teacher cared about him and how hard she worked to try to put up with his behavior while still improving it.
I pointed out to him that I had a duty to perform and a job to do. I told him parts of that job were wonderful and I loved them. I also pointed out the parts of my jobs were unpleasant and I wished that I did not need to do them. But, I concluded, if it comes down to doing my job or not doing my job, I will do my job.
I asked him not to make me choose between doing my job by expelling him from school or failing to do my duty, because, if he forced that choice on me, I would do my duty however much I disliked doing so.
This worked surprisingly well. He didn't magically get better, but his behavior did steadily improve. Until one day he broke a rule so basic that it could not be ignored or tolerated. I made no secret of the fact that I believed that kids belonged in school and that they should not be expelled unless it was absolutely necessary, and that in this case it was absolutely necessary.
Oddly, he even agreed with me. Sometimes I wonder if he did it deliberately, but then I wonder why he would do that. I suppose I'll never know. The point is, I warned him that I would do my duty however reluctantly. For a while that worked, but in the end he pushed me beyond the edge and I did what had to be done.
I was true to myself. I did not pretend to be somebody I was not. But in the end, I did what had to be done.
My advice is, do the same.
Acknowledge that you are a nice guy type who doesn't like being heavy handed, but add that you will be just as tough as your duty and his attitude force you to be. The choice is his, let him make it and live with the consequences.