Regolare i Conti

Both loyalty counters must be put onto the same planeswalker.

If the target creature is an illegal target by the time Settle the Score tries to resolve, the spell doesn’t resolve. You won’t put loyalty counters on a planeswalker.

You don’t choose which planeswalker receives loyalty counters until Settle the Score resolves. If you don’t control a planeswalker, you’ll simply exile the target creature and not put loyalty counters on anything.