MacBook Air dented bottom right corner

If it is a 2013-2017 MBAir, then you need to remove the Bottom Case & Battery. You will need to use a pair of pliers or a vice which need to be wrapped to protect the MBAir finish. You need the pliers/vice clamped near the bend and inline with it. Aluminum is soft so it doesn't take much pressure to straighten the case. Chances are the Bottom Case is also bent. It can be really difficult bending the Bottom Case to make it fit properly without gaps because of the multiple curves found on the corner. The trick to the bottom case is very small & gentle nudges.

Take it to the Apple Store or Authorized Apple repair center for an estimate. My guess for a Top Case & Labor will be $250-$300. Apple may want to replace the Bottom Case as well, though an independent repair center may be willing to straighten it.

I should add that when you bend the palmrest that you do not push on the display at all. Be careful not to damage the display or hinges in the process of straightening the corner of the palmrest.