Uhm, how can I lock a member's profile?
 

I've got a troublesome member on my site, and I want to prevent him from changing his custom user title and avatar, can I do with WITHOUT creating a specific USERGROUP for this member?

troublesome member?... kick/ban...

ok, next!

Nah I don't want to ban the dummy, he's comic relief on our forum, but I want to remove certain privileges that other members have, like changing the custom text and avatar.

so create a new usergroup for him...

see, if you'd do it at first, instead of posting here, you would have finished already.. :)

Create a condition that removes the edit button for him on whatever page you want to. Or a plugin that gives him a No Permission if he tries to access certain pages to change things.