ChaosK
[13] Hero
Then you're not having trouble,
. You're having trouble with the SCH mixup. UnseenWombat is correct, AAB or A:6 can beat out [3]B, B, but the opponent won't keep doing that string if you keep punishing it. They will use other moves from the stance such as SCH K (quick knees), SCH A (horizontal high stepkill), or the change to BH (the stance where it looks like Sieggy is chilling) where he can crouch your highs.
Essentially you're going to need to read your opponent and adapt. Take note of which move the opponent goes for regularly after [3]B (e.g. SCH B), then apply an appropriate response.
Possible responses to [3]B
Sieggy: SCH B = Natsu: AAB or A:6
Sieggy: SCH A = Natsu: Distorted Breeze (2B+K) or any TC move
Sieggy: SCH K = Natsu: Distorted Breeze (2B+K) or any SS move
Sieggy: BH = Natsu: A+B (perform after the BH GI effect though)
Actually AAB and A:6 beat all the options you mentioned, so its actually not a mixup and guaranteed.
The thing is A:6 only is guaranteed if you actually do hit the JF, so its really important that you learn to get it consistently.
AAB beats all options too (its faster than SCH A, B and K) and SBH does not activate in time for the GI or TC (its i9) BUT as Unseenwombat mentioned he can read you correctly and cancel his stance into 3B (the second 3B is necessary or the second hit of AA will hit him). If he TCs your AA you were too slow.
66B and bomb are good but against 66B he could do 2B+K and whiffpunish and bombs might get interrupted.If he uses 3B at tip range you can also try to backstep, it should evade everything he can do.
Then Whiff punish with 66B or Bomb.
JG is also helpful because he has no low from Chief Hold although it hurts if you miss the timing
And when going for JG you may give him the chance to stance dance.
Afaik 66K should beat all options.