wheel wobbles very bad

sometimes you can...

if the rim 'wobbles' in 2 directions over a very short section (over to one side then over to the opposite side of the bike right after, hitting one brake pad then the other) chances are good that you cant salvage the wheel.

if the rim 'wobbles' over to only one side you can diagnose how bad it is by loosening the spokes at that spot on the same side, if it still 'wobbles' over to that side, loosen some more, when the spokes opposite the 'wobble' are very loose (little or no tension) chances are good that you need a new rim or wheel.

inexpensive wheels we usually replace the wheel, expensive new wheels we normally replace just the rim and expensive older wheels we usually replace the rim and spokes.

if the 'wobble' disappears after loosening the spokes just a little then the wheel can probably be salvaged...

many bike shops I have dealt with will diagnose this for you for free...

If there is a dent towards the axle then it will be hard to fix. If it's a side-to-side wobble then it can be improved by adjusting the spoke tension so as to straighten the rim.

As said previously...sometimes a new wheel or rim is the cost-effective answer.