Bulk delete bogus admin accounts following hack?

[r5e]

Yes, I do have access to phpMyAdmin. I had considered this was probably the easiest option, but every official answer I always see to this suggestion is not to delete users directly from the database as it can cause problems.

I'm not 100% confident in exactly how to do it from phpMYAdmin. I can look at the table "user" on my database, select "search" and then in the "username" column, select "=" and type "supportvb" This will return me a list of all of these users. I then click on "select all" and then delete. Is this correct? It seems simple, but I didn't want to trash my DB through lack of knowledge on this. Appreciate if someone can confirm, or provide me better instructions.

--------------- Added [DATE]1382260489[/DATE] at [TIME]1382260489[/TIME] ---------------

Just did some other research and found someone else with a similar requirement. I modified their query slightly and I got the following:

UPDATE user SET usergroupid =17 WHERE (
CONVERT( `username` USING utf8 ) = 'supportvb'

I ran this via phpMy Admin. This looked for the username "supportvb" (which was the hack that inserted itself hundreds of times into the admin group) and then changed the group from 6 (admin) to 17 (a new group I created for this).

I now see the numbers in my Usergroup Manager reflect this. I check on one of the supportvb users and I can confirm that the group is no longer Admin, and the primary usergroup for these accounts is now the new group I created for them.

I now use the pruning system to clean up the rest. However, I find that when I search on this new usergroup, all the supportvb users show there, but they have 2 groups listed - the new one I just modified them to and also moderators. The "!" still appears on every account and it will not let me prune them.

What did I miss?