I think we should all take a new look at nair. A couple weeks back I started practicing nair so that I would know what direction they would be knocked in on the final hit and while it can be ambiguous to spot most of the time it's fairly easy to do so. Being able to nair into grab followups is pretty amazing, and it's led to me actually using nair with the intent to attack with the last hitbox against players now (something that just felt natural after my downtime). It seems way more effective than it should be, probably due to the hitbox being much larger than people expect. Like I've said before too, final hit nair as an edge-guard is devastatingly good due to it sending opponents at a downward angle. Against Fox and Falco it's pretty much a guaranteed KO at almost any percent if they get hit with that offstage.
Speaking of Fox and Falco, that downward angle is also effective in combos. This is untested in a real match, but if you get a grab at low percent, an upthrow > fair > nair is possible to combo depending on DI. If they are hit off the stage with that they will fund themselves quite low underneath the stage, a lot more than I expected. It's situational and highly dependent on DI, but it's very likely to end in a KO if you edgeguard and might even would set up for a final hit nair edgeguard. Also, if they don't DI the way you want you still have access to traditional upthrow > fair shenanigans, so the trade off isn't that bad at all.
In general, nair has always been a move that can intercept a ton of things, racked up damage, and in general was just super annoying to opponents. Now, I think it can be used to control your opponent as knowing which direction they will be knocked back allows you the chance to put yourself in a strong position to follow up, and really just give you a ****load of momentum. It's fairly low risk and the reward is quite high. Compared to M2's other neutral tools, nair might be the best one, at least it's damned good in so many situations.