How much force does my 2d ball need to fly from point A to B ?

The problem is that there's an infinity of different paths the player could send the ball that would pass through point B. If you fire it with an extremely large force, you can basically shoot straight at it.

You can limit the time it will take to reach B, or the maximum starting velocity, or the angle, but you need to give more information on what do you want the ballistic trajectory to look like.

After that, it's basically simply looking for a parabola that passes through two points, it's an easy mathematically problem.