Look for the following element in the MasterPage code:

<SharePoint:UIVersionedContent UIVersion="4" runat="server" id="PlaceHolderQuickLaunchBottomV4">
<ul class="s4-specialNavLinkList">

Above the bold section, add the following line of code:

<Sharepoint:SPSecurityTrimmedControl runat="server" PermissionsString="ManagePermissions">

Change the blue PermissionsString value to whatever you want. Multiple permissions can be separated with a comma (no spaces). Note it should be a permission your target user(s) do not have, and has to come from this list. Spelling and case-sensitivity is important. Finally, add the closing tag after the SharePoint:UIVersionedContent closing tag: