I always thought waveshine with walks instead of dashes was guaranteed in NTSC on Marth. While I would like to just throw this in and see what the consensus is, it would probably result in two parties stating contrary claims, so I guess I better cut this and go straight to TAS tests. Sigh …
Angles assume Fox is waveshining Marth from right to left. Unfavorable factor, favorable factor, bad outcome, good outcome.
Shine 1
1.1 • No SDI by Marth, 197° wavedash, walkfast afterwards: 8 frame window for shine 2.
1.2 • No SDI by Marth, 197° wavedash, dash→run afterwards: 5 frame window for shine 2. Frame 5 of this window will be a reverse hit.
1.3 • No SDI by Marth, 225° wavedash, dash→run afterwards: 5 frame window for shine 2.
1.4 • 1SDI+ASDI with 180°, 197° wavedash, dash→run afterwards: 5 frame window for shine 2.
1.5 • 1SDI+ASDI with 180°, 225° wavedash, dash→run afterwards : 2 frame window for shine 2.
1.6 • 1SDI+ASDI with 180°, 197° wavedash, walkfast afterwards: shine 2 whiffs.
1.7 • No SDI by Marth, 225° wavedash, walkfast afterwards: shine 2 whiffs.
1.8 • 1SDI+ASDI with 180°, 225° wavedash, walkfast afterwards: shine 2 whiffs.
At this point, we can already establish that perfect wavedash to walkfast is not reliable because Marth can SDI out. Wavedash to dash→run, on the other hand, is perfectly reliable. Even if the wavedash is as imperfect as 225°, it will still connect on a SDIing Marth.
You might wonder about the risk of overshooting against a Marth who SDIs in as a sort of counter against your wavedashrunshine. I didn’t include this option in the list because it hardly changes anything – even if you do a 197° wavedash and then dash, you have 3 frames to hit him forward and 2 frames to hit him backward with your shine 2, so all his SDI in will do is add another frame at the end that will hit reversed compared to 1.3.
The hard part about the wavedashrunshine is that you need to have a precise timing on the dash. If you dash 5 frames later than possible, your run will start to late and Marth can shield.
Shine 2
2.1 • No SDI by Marth, 197° wavedash, walkfast afterwards: 8 frame window for shine 2.
2.2 • No SDI by Marth, 197° wavedash, dash→run afterwards: 5 frame window for shine 2. All frames of this window will be reverse hits if shine 1 hit out of run. If shine 1 hit out of walk, the first 3 frames will not hit reverse.
2.3 • No SDI by Marth, 225° wavedash, dash→run afterwards: 5 frame window for shine 2.
2.4 • 1SDI+ASDI with 180°, 197° wavedash, dash→run afterwards: 5 frame window for shine 2.
2.5 • 1SDI+ASDI with 180°, 225° wavedash, dash→run afterwards : 5 frame window for shine 2.
2.6 • 1SDI+ASDI with 180°, 197° wavedash, walkfast afterwards: ~5 frame window for shine 2 depending on the exact precurring action. If shine 1 was hit from a walk, it will whiff.
2.7 • No SDI by Marth, 225° wavedash, walkfast afterwards: ~5 frame window for shine 2 depending on the exact precurring action. If shine 1 was hit from a walk, it will whiff.
2.8 • 1SDI+ASDI with 180°, 225° wavedash, walkfast afterwards: ~1 frame window for shine 2 depending on the exact precurring action. If shine 1 was hit from a walk, it will whiff.
Shine 2 (after frame 5 of 1.2)
Because reverse hits make you move left while Marth is moving to the right, only dash→run will reach him in time. Walking out of the (backwards) wavedash is not possible because it requires the entire turn animation (11 frames) to complete before it can start. Turning around earlier during shine takes way too long.
Waveshining Marth indefinitely
1. Start the waveshine with 1.2.
2. Continue with 2.3 to ensure you don’t hit reverse.
3. Repeat 2.3 until your next waveshine is the last that ends before the edge.
4. Do 1.2 again and hit the shine quite late during your shine to force a reverse hit.
5. Do a backwards wavedashrunshine and repeat steps 2-4 to the other side.
6. Repeat forever and finish with an upsmash.
This is inescapable. Marth can’t even change hit orientation by SDIing away from you when you need to hit reverse.
Edit: Because I tested this with debug mode’s frame advance, damage staling might make a difference.
Edit2: It seems move staling only changes the amount of hitlag and the damage of Fox’s shine. Hitstun and knockback are unaffected.
A completely stale shine has 1 frame advantage from electric hitlag opposed to 2 when fresh. This should reduce the frame window for wavedashrunshine from 5 to 4 – nothing dramatic.