Just another debate thread, only it includes two ships from one universe: Star Trek.
The Scimitar, headed by Shinzon, packs all the firepower it has - 50+ disruptors, and nearly 30 photon torpedoes. Plus, don't forget that planet-deadly thalaron radiation weapon. Also, it has the ability to cloak itself, rendering it invisible both to sensors and visual contact (unless hit by a phaser or weapon, which it will be temporarily revealed).
The Narada, on the other hand, is lead by Nero, a mad, bald captain (similar to Shinzon, only much more sinister looking than that teenage kid) packs all the firepower it had to destroy 47 Klingon warships and, of course, red matter. (actually, that's the big, scary spiky black ship you see in the new ST movie)
Given the sheer size of the Narada, I still think the Scimitar would at least be able to do a significant effect on the Narada given its thalaron radiation weapon and cloaking technology (however, it COULD be blasted away to bits before it fired its superweapon considering it took 7 minutes to charge it up).