Mega Destruction Dark Ball of Darkness and Destruction

What a friendly old man tends to use to convince people to help him with something that will help humanity as a whole.

Old man: X-BLADE!
(Please use the darkness.)

Disobedient teenager: Why would I use the darkness?

Old man: X-BLADE!
(Because it's for everyone's sake.)

Teenager: Okay I DON'T believe you.

Old man: X-BLADE!
(Mega Destruction Dark Ball of Darkness and Destruction)

Teenager: Ouchi ouch!

Old man: X-BLADE!
(Use the darkness.)

Teenager: okay sure

Old man: X-BLADE!
(You will even get my expert diplomatic skills by using it)

Teenager, who is also an old man now: X-BLADE!
(Okay I believe you.)