Is this the best of all possible worlds

As Leibniz would have us believe?

Many theists have argued, in defence of their god, that this world is fine tuned for life. They tell us if any one constant was altered, the world as we know it would disintegrate.

If we consider the above, does it make this world the best of all possible worlds or the worst, if changing any constant would lead to its collapse not into a worse world or a better world but total collapse?

In my opinion, if it was the best of all possible worlds, the changing of a constant would lead to the formation of a worse world.

What say you?