Pass attack from behind

I'll soon fix these guys

Wave a temporary goodbye to the Marines if any, fly back though the pass, land outside and attack in whatever fun-filled manner takes your fancy. They'll fire back if you get close, but they won't come out after you unless in rage mode, so feel free to keep your distance if you like. Once they're dealt with, head on through to tackle the rest of the enemy. When you reach the end of the pass, you may well hear the sound of your Marines starting to fight their way up the spiral path, homing in on you now that you're getting close again. They'll probably need your help, and fast!

Chain reaction fodder

When I was playing this on Legendary, there was a huge mass of enemy crammed into the pass. It was a lot of fun sniping loads of Grunts and Elites to litter the ground with plasma grenades, then setting off colossal chain reactions, some of the biggest you'll see in the entire game (and certainly far in excess of what you'd normally see). "I almost feel sorry for 'em", as that Marine says. You could ensure that you get a big mass of enemies by having a blockade at the pass exit, as described in my pass blockade rumble plan.

Jackal racket

If you get up close to the pass, loads of Jackals are liable to start up with rapid fire making a heck of a racket, but you can avoid most of it by moving side to side. It's quite good fun to experience, and sometimes you'll see enemies shoot each other in the back, which is always entertaining.

This should do the job

Scorpion carnage

You can even attack with the Scorpion, which you could've left nearby in advance (see my advice on rearranging), or which you could simply go and fetch. The huge blasts make a fine old mess in that crowded pass. If you want a long spell of Scorpion fun, fly back past the underground bridge to trigger a tunnel checkpoint but delay it with Banshee fire until you're back near the Scorpion (but you'll need to be safe enough from enemies that the game will give you the checkpoint). You'll then be able to keep reverting to that checkpoint.

Up on the pass entrance rock

Just at the start of the pass on the left, there's a large rock which is often climbable. Even if it's not, you could always drop yourself off on top with your Banshee of course. From up there you can have fun peeking your head over and whittling down the enemy at relatively close range. Watch out for Hunter shots mind; they can do serious damage even if they only hit on the other side.