I don't keep track of "epic" one piece panels.
But this was nothing special IMO. In fact, I don't even like it much tbh. Too chaotic and not very clear.
Considering how long the series is, I wouldn't even put this in top 100.
Unclear mid drawing, with no impressive visual impact. We, as readers, are to assume this is super impressive given the big dogs involved. But I just don't feel it.
Compare this to the panel of Whitebeard punching Akainu, with the marineford building collapsing due to the impact. 100x better than this panel.