You asked me ingame, so I explained then but it still did not work for you.
So I took your replay and started editing +/- from when you launched of the ground.
I think you should look closely at were my foot hits ( and especially angle of the leg, it sort of cuts trough it like a knife ), pause the replay many times around
the moment of impact to look at the joint settings ( so you can understand what happened ) then try to get thesame ( or better result ) starting with editing from 10 frames before impact and so on and so on.
I believe that if you do these things and really pay attention whilest doing them.
You will understand boomhits in no time, it is all about location of contact/hit/kick & the angle of the limb, rotation of your body, and when you stretch out to give you that slight extra mass behind the kick. Though I believe boomhits mostly happen because of the speed and rotation of the foot/fist because of the speed/rotation your foot/fist already cuts trough the joints without even stretching your own ( blow dealing ) limb, so directly after you can stretch out for that third/fourth etc etc dm
Good luck with it
Hope I helped you some.
PS: Put a pose in there as well if you would be wondering how you could land on your feet and stand still after that hard hit.