You can set an approval task to have more than one approver with a 'One Must Approve' option set.
When one approver approves the task the other approvers are not informed via email. If they attempt to approve via email they get a generic error, making no mention that it was approved. This can be especially important if they wish to deny for a given reason.
Can we either improve the reply error (giving information about who approved would be best) or email approvers when an approval is cancelled informing why.