@Alvin63 that user sounds like a nightmare. From your posts on here, he's certainly earned a sanction or two, or he's just gonna see you as weak and carry on undermining you at every turn - it's an ego trip for him, gives him a feeling of power that you let him get away with it. Classic troll behaviour.
Now, without having seen what your forum is, its subject and not having seen this member's posts, I don't wanna be too prescriptive by suggesting a long ban, or permaban, thread ban etc, but you do need to restrict him in some way for a time so that he starts to realise that he can't take the piss out of you and get away with it. And the restrictions should of course escalate if they carry on.
I had a user recently who was a bit like that, really hyper, all over the damn forum, and subtly and not so subtly dissing me, perhaps because I'm naturally quite easygoing. They were always paying
me so much attention rather than simply talking to me and others in a balanced manner like other members. They clearly thought I was a bit of a soft touch and some of my mods were going crazy for me to permaban him, but I said hold on for a bit to let them pay out enough rope to hang themselves with. I'd never had a user quite like this before and handling them was an interesting experiment for me. So, I kept the dialog going with them for a while giving them every chance to reform (which I knew they wouldn't) and also did restrict them for a while, too. Then, after they'd finally let out enough rope for them to clearly hang themselves with, I hit them with that lovely permaban after clear hints and warnings that they were out of order and a final message, which was just so satisfying! They clearly weren't expecting it and went mental trying to create new accounts to get round the ban, but either the forum autobanned them at registration, or I did from the approval queue and they eventually gave up and left us alone.
Moral of the story: you own the joint, you're the boss - never forget it.
Finally, if you want more specific advice or suggestions, or just to talk more about it in a more detailed way perhaps, please feel free to pm me with the forum link, the user and more details and we can chat.