Couple of points for clarification here: It’s Orberg LLPSI Cap XLIII
Tullus has just told his army in a way that will be heard by the enemy that he has ordered the treacherous Albani (led by Mettius) to attack the Fidenates from the rear. The text seems to say that he gave this order in such a way that the Fidenates could hear him - which I find perplexing. The enemy referred to in …ut hostes exaudirent would appear to be the Fidenates …magna pars Fidenatium Latine sciebant.. as the 2ns paragraph informs us.
In the 2nd paragraph we have …Tullus, fusoque Fidenatium cornu, in Veientes alieno pavore perculsos ferocior redit. What does alieno pavore mean here?
Finally we have Non alia ante Romana pugna atrocior fuit. Orberg tells us that ante here is an adverb meaning antea. However I take it that alia and Romana are adjectives describing pugna. So ante here would have the meaning of ever. No Roman battle was ever more violent
Primo Romani qui Albanis proximi steterant mirabantur, cur socii a lateribus suis digrederentur. Inde eques citato equo nuntiat regi ‘abire Albanos!’ Tullus equitem clara increpans voce, ut hostes exaudirent, redire in proelium iubet: ‘nihil trepidatione opus esse; suo iussu circumduci Albanum exercitum, ut Fidenatium nuda terga invadat!’
Terror ad hostes transit: et audiverant clara voce dictum, et magna pars Fidenatium Latine sciebant. Itaque, ne subito impetu Albanorum intercluderentur ab oppido, terga vertunt. Instat Tullus, fusoque Fidenatium cornu, in Veientes alieno pavore perculsos ferocior redit. Nec illi tulere impetum, sed ab effusa fuga flumen obiectum a tergo arcebat. Quo postquam fugientes devenerunt, alii arma foede iactantes in aquam caeci ruebant, alii dum cunctantur in ripa inter fugae pugnaeque consilium oppressi sunt. Non alia ante Romana pugna atrocior fuit.