Find anyone willing to buy your coin and sell it. Don't tell me you thought that the only way cryptos can be traded is thru exchange alone? Make sure you trading with escrow service since there is always scammer looking for quick bucks.
Seems like you didn't know this project. Batcoin is an abandoned project, so, if he will sell it to someone else, I don't think that there is someone who is willing to buy a useless coin. P2P is not an option here, he needs to move on since there is no way that a dead coin will be revived. All he has right now is just a shitcoin.