I used to do Air drop and bounty. Get all coins in time when the market is down. The value of all these coins lost 90% even now looking at it I do not believe it is no longer valid.
I cannot sell them because no one buys them, and its value can only be enough to transfer to exchange.
So do you have a way to hide it or delete all the coins from your wallet?
The only way to do that is to burn it if it irritates you however you'll need to spend Ethereum for each of transfers which is not worth it just to make yourself more feeling organized with your wallet. Alternatively, you may just move all of the valuable altcoins to a clean wallet including your ETH and then keep the old wallet thus you can still open it in case some grabage coins appear to have a great value to the market.