<label for="reenter_password" class="reenter_password{rm:hasError(property:'reenter_password',then:' text-danger')}">
    Reenter Password*
</label><br>
<f:form.password name="reenter_password" id="reenter_password"/>

/**
 * Complete New User Registeration
 *
 * @param User $newRegisteredUser
 * @validate $newRegisteredUser RMRmRegistrationValidationValidatorNewRegisteredUser
 * @validate $newRegisteredUser RMRmRegistrationValidationValidatorCompleteProfileUser
 */
public function completeNewRegisteredUserAction(User $newRegisteredUser)
{
    // Store Changes, Update and Persist
    $newRegisteredUser->setPassword($this->saltThisPassword($newRegisteredUser->getPassword()));
    $this->userRepository->update($newRegisteredUser);
    $this->objectManager->get('TYPO3\CMS\Extbase\Persistence\Generic\PersistenceManager')->persistAll();
}

TYPO3CMSCoreUtilityGeneralUtility::_POST()['tx_rmregistration_registration']['reenter_password']

// Compare Entered Passwords
if ($user->getPassword() == $user->getReenteredPassword()) {
    return TRUE;
} else {
    return FALSE;
}