Then just refuse to understand the task which is being given to you. They can't sue you because you suddenly become stupid. Do it until your KPI is 0 and then your company has no other option then to fire you.
This and quiet quitting are both reasons they can sue someone.
I don't believe that you can sue anybody for underperforming.
Sueing someone because he/she doesn't follow your orders.
I don't understand them, so I can't follow them. You can't sue somebody for being stupid.