"Ragnarok" has a pretty big, and old, battle.
Plus "Battle Lines" (Voyager#18) has the Voyager and crew drafted into an alien war, with everyone, except Janeway, as I recall, assigned to different alien ships.
"Cathedral" also features a major battle.
But with Shatner, he also co-wrote a Mirror Universe Trilogy that is probably the best Mirror Universe story out of all the MU stories. But how would you like to see the Klingon/Cardassion Alliance try to take over the Federation with the help of Kirk's doppelgänger, Tiberius Kirk?