>>530907846
if they're just jumping around trying to stay away from you the trick is often to dash jump up at them while trying to get directly under, wait half a beat then double in their direction to line up and hit 6/4H right as your character touches theirs
generally you want to be mostly underneath them basically with your head at their knees because throwable hurt/collision boxes reach really low and the grab hitbox is baised high
If they double jump to try to get away you can usually chase them down since throws hit so high, and if they don't and just block assuming you're trying to air to air you can still grab if you end up on the same height as them. If they have a good button that hits below them like Johnny j.H they can hit it to stop you but that's risky and hard to time, be patient and the situation is in your favour.