Mitsu has certain high strings like 11ba, and his stance "high/lows and low/highs", all these can be 4B'd with good reaction/anticipation and punished HEAVILY, and most of his stance mids are very punishable. 2KB, like Trolt already said, is a free 4B on punishment.
WHERE'S THE 6K?!?!?! All those mixups that got started by mitsu being in your face and at advantage? 6K will either score you a CH becuase you TJ'd the 2KB/low, or just give you minor "juggle" damage instead of a brutal combo. 6K is Raphael's savior, and you barely used it.
4Bing randomly vs Mitsu(we have a habit of getting greedy with 4B because it's Raphael's only means of NH combo damage, and it'll get us all killed...) or at mid range isn't recommended, I have a video in this same thread vs Xeph where I got raped a ton for doing that.
Anytime you're looking for i16 punishment, use 3B over BB, reason being? BB leaves you at -2 and deals 30 dmg, whiled 3B prep BB leaves you at neutral(I believe....), and deals 38 dmg, with a prep continuation to play with(use sparingly). You can also vouch to lose the guaranteed 18 damage off the prep and try a prep mixup, but I rarely do this as well.
YOu HAVE TO UTILIZE RAPHAEL'S 6BB. This is one of the longest range, i13's in the game, and can interrupt all kinds of shit and put you back at advantage(or neutral....because Raph's frames suck for this move). Raphael has all sorts of -2's or less on block(66A+B, 6A, A, SEA A, SEB anything) 6BB is always going to be a CH on any immediate counter strike that is i16 or slower and doesn't TC.
6A is alright...it's a cute 1-2 combo oh CH(CH 6A, 2B), but 34 dmg at best, high, only tracking strong side, and i15?(6BB is i13 with 3 or 4 TIMES the range and multiple options to finish it)....it's nothing special. -2 on block is it's real shining glory, but at the range and lack of spacing(on block, the spacing on NH is great...) it has, Raph isn't in a comfortable -2 position(unlike 66A+B, he can't 44B everything)
I honestly have trouble utilizing 4K....does it REALLY catch all step? Because I seem to whiff with this move alot.....and it doesn't seem to track as well as people say....I've yet to implement 4K into my game well, and according to the properties of this move that are discussed by Mandritti, THERE'S NO REASON I shouldn't...but I've NEVER been able to make it work for me...