He walked away with $2.15M and didn't have to play a down.
"What seems to have happened is that Athletes First negotiated a new contract for Incognito, he now wishes he hadn’t signed that contract, he knows he can’t get out of the contract by retiring because then he’d have to pay back his signing bonus, and now he wants the Bills to cut him so he doesn’t have to pay his signing bonus."
https://profootballtalk.nbcsports.com/2018/04/15/richie-incognito-asks-to-be-released-from-his-contract/