For good
Definition 1 of 2
Pro Tip 1/3Finality
Indicates an action that won't change or can't be undone. 
After the argument, she decided to leave for good.
Pro Tip 2/3Dramatic Decisions
Often used to emphasize serious, life-changing decisions. 
He quit his job for good to start a new adventure.
Pro Tip 3/3No Return
Emphasizes there is no intention to return or revert. 
The shop has closed down for good.