In the right-hand corner, Magneto has an semi-unblockable c.hp (among other things) on some characters. Easiest way to set it up is to do ROM, ending with 3 hits instead of 2 hits after the ad if they’re too low, land, walk forward a bit, c.hp ^ (up-back) sj.hk addf sj.d+lk sj.mk repeat. It’ll work for sure on Mag because you can vary the timing so that it’ll hit regardless of the way they block. You should be able to do it on Storm, too, but the timing is a little trickier.
Haven’t tried on Cable, Capcom, Cyke, Sent. It’ll probably work on all of them if they block the regular way, but I don’t know what’ll happen if they block the other way. Also doesn’t work on the left side of screen (kinda like Storm’s airborne LA into the wall).