PHP Code:

select u.id,u.username,u.last_online, u.admin, u.country, uv.location, u.favoritegame from `users` as `u` left join `users_visits` as `uv` on u.id = uv.user where u.last_online > date_sub(NOW(), interval $onlineinterval) group by u.id order by uv.id desc, u.last_online desc 


I need user_visits to be desc (by id), any advise?

You mean you need to have the rows from the table users ordered in a descending order by the counted number of visits that correspond to the numbers of rows into the table users_visits ?

If yes, this is totally not tested but might work:

select u.id,u.username,u.last_online, u.admin, u.country, uv.location, u.favoritegame 
from `users` as `u` 
  cross join (
    select count(*) as cnt
    from users_visits uv
    where uv.user=u.id
  ) as x
where u.last_online > date_sub(NOW(), interval $onlineinterval) 
group by u.id,u.username,u.last_online, u.admin, u.country, uv.location, u.favoritegame 
order by x.cnt desc, u.last_online desc

i need the group by to return 1 result in descending order. It seems to be returning ascending only.

group by and order are 2 different things.
A group by cannot give something in any order.
First, you get the rows you need (with a group by if needed), then you order those rows.

So, forgetting about the order, does your query gives you back the rows you want?
If not, it's the query that need works, not the order, and maybe not the group by neither.

What I'm trying to get at is group by obtains the first result in an ascending order, and returns only that in the group. No matter which order by.

If it were possible, group by desc would be what I'd be after.

I'm afraid you didn't understood me.
Without worrying about the order of the rows, does the query up there gives you the good rows or not ?

If it's just a matter of ordering, then it's nothing.
If you don't have the right rows, than there is something else to change in the query.

Again, a "group by" clause does not order anything.
You cannot order something with a "group by", you can only limit the number of rows you are getting back on a specific criteria.

So, if the rows are not those you expect, then the "group by" criteria is wrong.
If the rows are correct, then the "order by" clause need some work.
Maybe a sub query is needed to filter the group by result, I don't know.
It's up to you to tell me.

By the way, the table definitions and some sample datas would be of great help.