If you want to quickly reset a large number of passwords, you can use Powershell to do this. With a small adjustment, you can also read in a CSV file with users and reset the passwords to a default password:
$userlist= @() do { $input = (Read-Host "AD User") if ($input -ne '') {$userlist += $input} } until ($input -eq '') foreach ($user in $userlist) { write-host "Setze Passwort für $user" get-aduser $user | Set-ADAccountPassword -Reset -NewPassword (ConvertTo-SecureString -AsPlainText "MeinPasswort" -Force) }