Hey, so it looks like I'm late to the party but I'll try helping nonetheless. It looks like you want specifics so brace yourself...:
So in regards to Natsu's okizeme (which is bloody awful but I'm not here to rant about that), 2A+B (UA bomb) and 1A are good options when Natsu makes the read that the opponent is going to roll or tech.
You can get up and block low on
1A after almost every knockdown. After some knockdowns, 1A is guaranteed as a combo ender, so off of KNDs like 3KKK, 66B BE, AC (Air-Catch) A+B, AC A:6 etc. There are some situations where 1A is a combo unless you do a very specific response, e.g. a tech, so for example with her PO A:6 knockdown which you will often see in play as i16 punisher 6A+B4 PO A:6, 1A is a combo if you stay on the ground, but if you tech in any direction you can block it and then punish it hard (it's -26).
2A+B never actually combos, but because it is a fast UA (i45), it's always going to hit people unless they attempt to get up and JG it. The trade-off for this is how weak it is when it hits grounded players, they take something like 10 damage and they get pushed away from Natsu, so it puts them out of danger of further oki. A lot of players choose to take this small damage then get up safely. After a few knockdowns 2A+B will TT (Tech-Trap) for upwards of 75 to 110 damage depending on the combo Natsu does, this is why teching vs. her is usually a very bad idea unless you are confident she isn't going to throw down a bomb or something else that TTs.
4A+B (the pink bomb) is an option that lies somewhere between 1A and 2A+B in terms of its use. It's my preferred oki of choice most of the time because of how damn useful it is and the mix-ups you can force with it. If my opponent can't deal with PO correctly then I'm going to keep throwing 4A+B at them and putting them into uncomfortable situations. On the knockdowns I mentioned for 1A being guaranteed, 4A+B is also guaranteed at those same places, with the differences being slightly less damage, and the fact that it's weaker to tech because it is both slower and it lacks any horizontal aspect to it (1A is a sweeping low whereas 4A+B just comes down vertically).
The thing to watch out for with this move though is it does TT a lot, like if you back-tech after being hit by 66B BE, you will be launched by a 4A+B and end up taking more damage than if you got up into a 2A+B.
Getting out of PO mix-ups:
4A+B6 as oki is the purple bomb then the forward dash. At this point Natsu is in PO so she has to commit to a PO option, or try a dash-cancel, but this basically eliminates her oki advantage and gives time for the opponent to get up and prepare. Each of her PO options is strong in it's own way, but has a counter to it. The problem is a counter for one option might lose to a different option, so it's mix-up city:
PO B+K - block low then punish with FC B, or step then punish with a vertical that hits grounded (standard 3Bs, 2Bs etc.)
PO B - step then heavy punish (you have at least 30 frames of advantage to work with if she whiffs this), alternatively try JGing or GIing it, but it can be delayed so watch out for that.
PO A/A:6 - duck and WR punish (they are both highs), or if she does A:6 you can block punish with an i14 or faster. These will kill step however.
PO K - probably her best option, it beats everything as it is fast (i11), tracks step, has range and can burst. The way to deal with it is to block it then punish as it is -21. PO K and PO B can be used as mix-ups, you either block or step.
HOV B - step it and do a quick punish as it recovers fast.
HOV A - block low. It is safe so you can't punish it.
For both HOV B and HOV A, you can step and block low to avoid both of them, so as soon as you see her go into the air for HOV, do that.
TL;DR:
- Teching is almost always a bad idea unless you are confident Natsu isn't going to throw out a bomb or some other TT. Against a wall after her 3KKK knockdown, she can do 44KKK 1A off of the wall for extra damage, but she could do 2A+B if you tried to tech out of it, giving her more damage.
- Rolling after being knocked down will protect you from any TT attempts, but you will end up eating 1As and grounded bombs.
- Staying down is the same as rolling except you can react to and block 1A if you see it coming. The weakness here is bombs still hit you, but what is even more frightening is that Natsu can do 44KK on you for big damage, or SOTFD (21436B UA) for 70 damage.
- During a PO mix-up, step and block low to beat most options. If you keep getting hit by a tracking PO K, block it and punish it with an i21.
General advice for knockdown situations:
- 66B BE - take the 1A or 4A+B6 PO mix-up.
- 3KKK - 1A is guaranteed. Against a wall, consider teching to escape 44KKK, but keep in mind the risk of TT 2A+B.
- PO A:6 - back-tech to escape everything except a well-timed TT 66K for only like 38 damage.
- AC A:6 (commonly seen as 3B A:6) - same as above, back-tech escapes all except a hard-to-execute TT 66K. Side-tech also escapes a lot of stuff.
- AC A+B (commonly seen as bomb launch A+B) - take the 1A or 4A+B6 PO mix-up. Teching here is suicide, both bombs will catch techs.
- A+B - get up blocking, Natsu is too far away to tech-trap or hit you with anything unless she steps forward or tries an unsafe 1A.
- A:6 - same as above, you are safe to get up.
- 66B - same as above.
- 66AB - roll and take whatever she tries. 2A+B will launch you if you get up or try side/front-techs. 4A+B catches back-tech.
- 44A - back-tech escapes bombs but you will take a non-scaled 6K, so combined 44A 6K is about 54 damage.
- 44B - safe to get up. Jump the bomb on reaction.
- 6AK - same as before, except the bomb is harder to jump, but still possible.
- 6AB - roll, you can't jump the bomb in time if you stand up.
Those are the majority of knockdowns you will take vs. Natsu. If there's something you still need answering then feel free to ask. Maybe some 'experienced' Natsu players learned a thing or two from this as well. ;)
