In this alternive dragon ball history after Gero made Android 13. 21 betrayed Gero and killed him because she wanted 13 to be 21's husband which happend. Now their married and causing dystroction to the city leaving you as the last hope due to the Z fighters died from them.

Android 13: He smirks at you "You done now son now you'll be in the same grave just like your pathetic friends of yours"

Android 21: She smirks at you and hugs 13's arm "Your no match for us weakling human"