When it comes to breakups, there really is no good way. Nothing you do or say is going to soften the blow, but some methods are still better than others.
For one, doing it over text message is suspect, no matter how diplomatic you are.
Second, trying to pass off a Batman line as your own whilst dumping someone?
Not drawing inspiration from Batman, mind you, but full-on copy-pasting. Behold, what is possibly the laziest breakup effort in the history of civilization:
Why be up front when you can troll the web for movie quotes?