Viewing some of the replays (Boxer vs. Sakura), you nailed Boxer's combo into headbutt xx Ultra I in the corner and I noticed you pressed 6 light punches in the input display. As soon as you hit ultra I in the corner; press and hold lp during his two straight punches (first straight will juggle and then second straight will whiff), and then press and hold lk for his 3 remaining upper punches for the finish. If it's mid-screen to corner; press and hold lk for the juggle(for the first punch), and press and hold lp for the whiff (2nd punch), and press and hold lk for the remaining 3 upper punches. Or you can mix and match, the difference is by 2 dmg points, not sure. I'm not a frame data guy.
TL;DR or if it doesn't make sense.
Short version -
corner
- j.hk, c.lp, c.lp, c.lk xx hp headbutt xx ultra I - hold lk(or any kick) for first punch, hold lp(or any punch) for the 2nd punch, hold lk(or any kick) for the remaining punches - 383 combo dmg
-j.hk, c.lp, c.lp, c.lk xx hp headbutt xx ultra I - hold lp(or any punch) for the first two straight punches, hold lk(or any kick) for the last three upper punches - 381 combo dmg (I use this)
-j.hk, c.lp, c.lp, c.lk xx hp headbutt xx super - hold lk(or any kick) for all five upper punches (342/347/374/394 combo dmg - depending if I executed the super early or late) - Try it.
mid-screen
- j.hk, c.lp, c.lp, c.lk xx hp headbutt xx ultra I - hold lk(or any kick) for first punch, hold lp(or any punch) for the 2nd punch, hold lk(or any kick) for the remaining punches - 383 combo dmg (I use this)
- j.hk, c.lp, c.lp, c.lk xx hp headbutt xx ultra I - hold lp(or any punch) for the first two straight punches, hold lk(or any kick) for the last three upper punches - 381 combo dmg
-j.hk, c.lp, c.lp, c.lk xx hp headbutt xx ultra I/ or xx super - hold lk(or any kick) for all five upper punches - 387 combo dmg (394/401 combo dmg for super)
Never really thought about the differences in dmg. I've always used the ones listed above whenever I'm playing Boxer. If anyone else wants to correct me, please do so. Put me in my place, I don't care lol. I just tried it in training mode just now.