okay so A2L's suggestion is actually good and i only write this one in case someone gets frustrated trying it.
press and hold Dpad left or right (opposite your opponent) while u tap RB. get the timing down
i think the down thumbs for the usage of x is fair. i found RB worked 99% of the time. 100% at the time i got this achievement.
if this suggestion saves u the frustration then please give both of us a thumb up. i tried 100 things before i got this to work and wouldnt have tried again if not for his strategy having 22 plus ones. no other character was nearly this consistant.